Vehicle seat airbag system and vehicle seat

ABSTRACT

A vehicle seat airbag system includes an airbag which is caused by a vehicle seat airbag system to inflate and develop within a seat back. The airbag is disposed between a seat pad and a rear board provided in a rear of the seat back. Inflation and development of the airbag in the seat back allows the airbag to elastically support an upper body of a seated person, and causes the rear board to be pushed rearwardly to allow the airbag to elastically receive an impact force which is applied to the rear board.

The present application is a Divisional application of U.S. patentapplication Ser. No. 14/503,665, filed on Oct. 1, 2014, which is basedon and claims priority from Japanese Patent Application No. 2013-206794filed on Oct. 1, 2013, Japanese Patent Application No 2013-206800, filedon Oct. 1, 2013, and Japanese Patent Application No. 2014-163516, filedon Aug. 11, 2014, the entire contents of which are incorporated hereinby reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a vehicle seat airbag system and avehicle seat, and particularly to a vehicle seat airbag system and avehicle seat equipped with an airbag within a seat back of the seat.

2. Related Art

In a vehicle seat such as an automobile seat, an airbag system is knownthat protects a seated person against an impact at the time of acollision by inflation and development of an airbag which is disposed ina seat back

For example, the vehicle seat disclosed in Japanese Unexamined PatentApplication Publication (JP-A) No. 10-273000 includes a seat pad on thefront surface of an elastic installation supporting member which isinstalled inward of a seat back frame, and an airbag in a contractedstate is disposed in a space between the elastic installation supportingmember and a supporting plate which is disposed rearwardly of theelastic installation supporting member and has a robust structure.

With this vehicle seat, an operation of an inflator corresponding todetection of an impact greater than or equal to a predetermined valuecauses the airbag to inflate between the elastic installation supportingmember and the supporting plate so that rearward movement of a seatedperson at the time of a collision is elastically supported and regulatedfrom the rear, and the impact energy is absorbed by pressure reductionand contraction of the airbag.

In Japanese Unexamined Patent Application Publication (JP-A) No.2010-52621, a first airbag, which is designed to inflate and developtoward a seated person on the rear seat, is installed in the lowerportion of the rear surface of the seat back of the front seat, and asecond airbag in a flat state is disposed on the front surface of anelastic installation supporting member which is installed inside a seatback frame within the seat back of the front seat.

Consequently, an operation of an inflator corresponding to detection ofan impact greater than or equal to a predetermined value causes thefirst airbag to inflate and develop toward a seated person on the rearseat, thus even when the seated person on the rear seat is moved forwarddue to an impact at the time of a collision, the seated person isprevented from strongly hitting the rear surface of the seat back of thefront seat. Furthermore, rearward movement of the upper body of a seatedperson on the front seat at the time of a collision is elasticallysupported, regulated from the rear and protected by the inflation anddevelopment of the second airbag. The inflation timing for the first andsecond airbags is controlled, and an appropriate protection for a seatedperson is achieved.

As described above, the vehicle seat disclosed in JP-A No. 10-273000achieves the protection of a seated person on the vehicle seat by thepresence of the air bag and the supporting plate which is disposedoutward rearwardly of the air bag and has a robust structure. That is,the impact of rearward movement of a seated person is reduced by theairbag, and an impact applied from the rear of the seat back is receivedby the supporting plate and is absorbed by the airbag.

Therefore, when a rear seat is present and a seated person is on therear seat, a collision of the seated person with the front seat from therear of the seat back causes a large impact when the seated personcollides with the supporting plate. Therefore, an impact from the rearcannot be received softly, which may cause not only a damage to theknees of the seated person on the rear seat, but also a significantimpact to the person on the front seat.

On the other hand, according to the airbag device in JP-A No.2010-52621, protection of the seated person on the front seat andreduction in damage may be expected by the second airbag that inflatesand develops within the seat back of the front seat. Also, protection ofthe seated person on the rear seat is achieved by the first airbag thatinflates and develops toward the seated person on the rear seat.However, not only the airbag device needs to be provided within the seatback, but also the first airbag, which inflates and develops toward theseated person on the rear seat, needs to be separately provided in thelower portion of the seat bag of the front seat. Thus, the structure ofthe seat bag becomes more complicated and control load for each airbagincreases.

In addition, the first airbag significantly expands diagonally upwardfrom the lower portion of the rear surface of the seat back of the frontseat toward the seated person on the rear seat, and thus the inflationand development pattern becomes unstable, which does not providesufficient stability for accurately, reliably receiving a collision ofthe seated person on the rear seat with the seat back of the front seat,and for absorbing the impact.

As described above, in each structure of the above-describedconventional arts, there is a possibility of further improvement ondirect protection of the seated person on the front seat by the airbagand protection against an impact to the seat back from the rear byadopting a simple structure.

In a vehicle such as an automobile, such a collision of the knees of theseated person on the rear seat with the seat back of the front seat mayoccur not only at a front-end collision, but also in a situation wherethe seated person on the rear seat is pushed forward due to deformationof the rear part of the vehicle at the time of a rear-end collision andthe knees of the seated person strongly collides with the rear surfaceof the seat back of the front seat.

SUMMARY OF THE INVENTION

The present disclosure has been made in view of the above-describedproblems and provides a vehicle seat airbag system and a vehicle seatthat are capable of achieving direct protection of a seated person by anair bag at the time of a collision and accurate reduction in impact fromthe rear of the seat back without adopting a complicated configuration.

A first aspect of the disclosure provides a vehicle seat airbag systemincluding: an airbag which is caused by the seat airbag system toinflate and develop within a seat back. The airbag is disposed between aseat pad and an outer layer of a rear of the seat back, and theinflation and development of the airbag in the seat back allows theairbag to elastically support an upper body of a seated person and toelastically receive an impact force which is applied to the rear of theseat back.

The seat back may have a flexible member that covers a front of theinflated and developed airbag to allow the upper body of a seated personto be elastically supported, and the seat back may further have aflexible movable member that covers a back of the inflated and developedairbag to allow an impact force applied to the rear of the seat back tobe elastically received.

A second aspect of the disclosure provides a vehicle seat airbag systemincluding an airbag which is caused by the seat airbag system to inflateand develop within a seat back. The airbag is disposed between a seatpad and an outer layer of a rear of the seat back, and the inflation anddevelopment of the airbag in the seat back causes the outer layer toexpand rearwardly and allows the airbag to elastically support an upperbody of a seated person and to elastically receive an impact force whichis applied to the rear of the seat back.

The outer layer may have an elastic portion in an area corresponding tothe inflated and developed airbag.

At least an area of the outer layer may be composed of a material havingelasticity different from elasticity of the outer layer other than thearea which corresponds to the inflated and developed airbag.

The outer layer may have a gusset that enables rearward expansion of theairbag which is caused by the inflation and development of the airbag.The outer layer may have a breaking part that enables rearward expansionof the airbag which is caused by the inflation and development of theairbag.

The vehicle seat airbag system may further include a rear board that isdisposed rearwardly of the outer layer along an expansion area of theouter layer.

A third aspect of the disclosure provides a vehicle seat airbag systemincluding an airbag which is caused by a seat airbag system to inflateand develop within a seat back. The airbag is disposed between a seatpad and a rear board provided in a rear of the seat back, and theinflation and development of the airbag in the seat back allows theairbag to elastically support an upper body of a seated person, andcauses the rear board to be pushed rearwardly to allow the airbag toelastically receive an impact force which is applied to the rear board.

The rear board may be supported on the rear of the seat back swingablyin a direction away from the rear of the seat back.

The rear board may be removed from the rear of the seat back by thepushing.

The rear board may be removably fixed to the rear of the seat back andinclude: a collision prediction unit that predicts a collision to thevehicle; and a fixing release mechanism that releases the fixing basedon information of collision occurrence which is predicted by thecollision prediction unit.

An outer layer may be interposed between the airbag and the rear board,the outer layer being caused by the inflated and developed airbag toexpand rearwardly, and the outer layer may be provided with the rearboard.

The rear board may include a fragile part.

The vehicle seat airbag system may further include: a control unit thatcontrols the inflation and development of the airbag; and a collisiondetection unit that detects a collision to the vehicle. The control unitmay cause the airbag to inflate and develop after a predetermined timedelay since the collision detection unit detects a collision.

The vehicle seat airbag system may further include: a control unit thatcontrols the inflation and development of the airbag; and a collisionprediction unit that predicts a collision to the vehicle. The controlunit may start to cause the airbag to inflate and develop at a timewhich is determined based on a time of collision occurrence predicted bythe collision prediction unit.

The airbag may inflate and develop in multiple steps within the seatback.

An fourth aspect of the disclosure provides a vehicle seat including: aseat back frame, an elastic installation supporting member installed inthe seat back frame, and an airbag within a seat back, the vehicle seatcausing the airbag to inflate and develop within the seat back. Aninflator is attached to the seat back frame, and the inflation anddevelopment of the airbag in the seat back due to an operation of theinflator allows the airbag to elastically support an upper body of aseated person and to elastically receive an impact force which isapplied to a rear of the seat back.

The seat back frame may be formed in a substantially frame shape along aseat back shape, the airbag is provided in the seat back frame in asubstantially frame shape, and the inflator may be attached to a sideportion of the seat back frame in a substantially frame shape.

The inflator may be disposed within the seat back frame in asubstantially frame shape.

The airbag may be disposed in the vehicle body rearwardly of the elasticinstallation supporting member, and the inflator may be disposed in thevehicle body forwardly of the elastic installation supporting member.

The inflator may be disposed outside the seat back frame in asubstantially frame shape.

A fifth aspect of the disclosure provides a vehicle seat including: aseat back frame, an elastic installation supporting member installed inthe seat back frame, and an airbag within a seat back, the vehicle seatcausing the airbag to inflate and develop within the seat back. Aninflator is attached to the seat back frame, the seat back frame isformed in a substantially frame shape along a seat back shape, theairbag is provided in the seat back frame in a substantially frameshape, the inflator is attached to at least one of an upper portion anda lower portion of the seat back frame in a substantially frame shape,and the inflation and development of the airbag in the seat back due toan operation of the inflator allows the airbag to elastically support anupper body of a seated person and to elastically receive an impact forcewhich is applied to a rear of the seat back.

The inflator may be disposed within the seat back frame

The inflator may be disposed outside the seat back frame.

The inflator may be attached to a position near a side end of at leastone of the upper portion and the lower portion of the seat back frame ina substantially frame shape.

The inflator may be attached to each of the upper portion and the lowerportion of the seat back frame, and each inflator may operate with atime lag to cause the inflation and development.

The lower portion of the seat back frame to which the inflator isattached may be a cylindrical cross member that extends in a widthdirection along a lower side of the seat back, and the inflator may befixed to an inside of the cross member.

A sixth aspect of the disclosure provides a vehicle seat including: aseat back frame, an elastic installation supporting member installed inthe seat back frame, and an airbag within a seat back, the vehicle seatcausing the airbag to inflate and develop within the seat back. Aninflator is attached to the seat back frame, the seat back frame isformed as a whole in a substantially frame shape along a seat backshape, the airbag is provided in the seat back frame in a substantiallyframe shape, the inflator is attached to the seat back frame in asubstantially frame shape at a corner portion or a bending portionthereof, and the inflation and development of the airbag in the seatback due to an operation of the inflator allows the airbag toelastically support an upper body of a seated person and to elasticallyreceive an impact force which is applied to a rear of the seat back.

The attachment of the inflator to the seat back frame may be achieved bybridging the inflator between both side positions of the seat back frameincluding the corner portion or the bending portion.

The seat back frame may have a lower cross member and an upper crossmember that extend in a width direction at a lower and an upperpositions respectively, and a pair of side frames that are disposed onboth sides in the width direction. The corner portion or the bendingportion may serve as a connecting portion between the side frames andthe lower cross member. The inflator may be bridged between and attachedto the side frames and the lower cross member.

The seat back frame may have a lower cross member and an upper crossmember that extend in a width direction at a lower and an upperpositions respectively, and a pair of side frames that are disposed onboth sides in the width direction. The corner portion or the bendingportion may be located between the side frames and the upper frame. Theinflator may be bridged between and attached to the side frames and theupper cross member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic vertical cross-sectional view of a vehicle seatillustrating the outline of a vehicle seat airbag system according to afirst implementation;

FIG. 2 is a schematic perspective view with partial cutaway of thevehicle seat as seen from the rear;

FIG. 3 is an operation explanatory diagram of the vehicle seat when animpact occurs;

FIG. 4 is a control circuit block diagram of the vehicle seat airbagsystem;

FIG. 5 is a control circuit block diagram of the vehicle seat airbagsystem;

FIG. 6 is a schematic explanatory diagram as seen from the rear,illustrating the outline of a second implementation;

FIG. 7 is an operation explanatory diagram of the vehicle seat when animpact occurs;

FIG. 8 is an operation explanatory diagram of the vehicle seat;

FIG. 9A is a schematic explanatory diagram of the rear part of a seatback and FIG. 9B is an operation explanatory diagram of the seat back;

FIG. 10A is a schematic explanatory diagram of the rear part of the seatback and FIG. 10B is an operation explanatory diagram of the seat back;

FIG. 11A is a schematic explanatory diagram of the rear part of the seatback and FIG. 11B is an operation explanatory diagram of the seat back;

FIG. 12A is a schematic explanatory diagram of the rear part of the seatback and FIG. 12B is an operation explanatory diagram of the seat back;

FIG. 13A is a schematic explanatory diagram of the rear part of the seatback and FIG. 13B is an operation explanatory diagram of the seat back;

FIG. 14A is a schematic explanatory diagram of the rear part of the seatback and FIG. 14B is an operation explanatory diagram of the seat back;

FIG. 15A is a schematic explanatory diagram of the rear part of the seatback and FIG. 15B is an operation explanatory diagram of the seat back;

FIG. 16A is a schematic explanatory diagram of the rear part of the seatback and FIG. 16B is an operation explanatory diagram of the seat back;

FIG. 17A is a schematic explanatory diagram of the rear part of the seatback and FIG. 17B is an operation explanatory diagram of the seat back;

FIG. 18 is a schematic vertical cross-sectional view illustrating theoutline of a vehicle seat according to a third implementation;

FIG. 19 is a schematic perspective view with partial cutaway of thevehicle seat as seen from the rear;

FIG. 20A is an enlarged view of portion a of FIG. 18 illustrating theoutline of a rear board supporter and FIG. 20B is an enlarged view ofportion b of FIG. 18 illustrating the outline of a rear board retainer;

FIG. 21 is an operation explanatory diagram of the vehicle seat when animpact occurs;

FIG. 22 is a schematic explanatory diagram illustrating another exampleof the third implementation;

FIG. 23 is a schematic vertical cross-sectional view illustrating theoutline of a vehicle seat according to a fourth implementation;

FIG. 24A is an enlarged perspective view of portion c of FIG. 23illustrating the outline of a rear board supporter and FIG. 24B is anenlarged view of portion d of FIG. 23 illustrating the outline of a rearboard retainer;

FIG. 25 is an operation explanatory diagram of a vehicle seat when animpact occurs;

FIG. 26 is a schematic vertical cross-sectional view illustrating theoutline of a vehicle seat according to a fifth implementation;

FIG. 27 is an operation explanatory diagram of a vehicle seat when animpact occurs;

FIG. 28 is a schematic rear view with partial cutaway for explaining asixth implementation;

FIG. 29 is a cross-sectional view of FIG. 28 taken along line XXIX-XXIX;

FIG. 30 is a schematic cross-sectional view of a vehicle seat accordingto a seventh implementation;

FIG. 31 is a schematic perspective view with partial cutaway of thevehicle seat as seen from the rear;

FIG. 32 is an operation explanatory diagram of the vehicle seat when animpact occurs;

FIG. 33 is a schematic perspective view with partial cutaway of avehicle seat as seen from the rear according to an eighthimplementation;

FIG. 34 is a fragmentary perspective view with partial cutaway of thevehicle seat;

FIG. 35 is a schematic rear view with partial cutaway for explaining amodification of the eighth implementation;

FIG. 36 is an operation explanatory diagram of the vehicle seat when animpact occurs according to a modification of the eighth implementation;

FIG. 37 is a schematic cross-sectional view of a vehicle seat accordingto a ninth implementation;

FIG. 38 is a schematic perspective view with partial cutaway of thevehicle seat as seen from the rear;

FIG. 39 is an operation explanatory diagram of the vehicle seat when animpact occurs;

FIG. 40 is a schematic perspective view with partial cutaway of avehicle seat as seen from the rear according to a tenth implementation;and

FIG. 41 is a schematic cross-sectional view of an operation state of thevehicle seat at the time of an offset collision, the cross-sectionalview corresponding to a cross-section along line XXXXI-XXXXI in FIG. 40.

DETAILED DESCRIPTION First Implementation

Hereinafter, a first implementation of a vehicle seat airbag systemaccording to the present disclosure will be described with reference tothe accompanying drawings. FIG. 1 is a schematic verticalcross-sectional view illustrating the outline of a vehicle seat; FIG. 2is a schematic perspective view with partial cutaway of the seat for avehicle as seen from the rear; and FIG. 3 is an operation explanatorydiagram of the seat for a vehicle when an impact occurs. It is to benoted that arrow F indicates the forward direction of the vehicle andarrow W indicates a vehicle width direction in each figure.

As illustrated in FIG. 1, a front seat 10 and a rear seat 60 aredisposed in parallel at the front and rear as vehicle seats on a floor 1in the vehicle cabin. The front seat 10 has a seat cushion 11 that issupported on the floor 1 and supports the buttocks of a seated personPf, a seat back 20 that supports an upper body Pb which is from a waistto a chest of the seated person Pf, and a headrest 40 which is locatedupwardly of the seat back 20 and supported on the seat back 20. Althoughthe seated person Pf may rest a head Ph on the headrest 40 while drivinga vehicle, this posture makes it difficult to perform drivingoperations, and so normally, the seated person Pf is seated with thehead Ph slightly away from the headrest 40.

As illustrated in FIGS. 1 and 2, in the front seat 10, a plurality ofelastic installation supporting members 27 is provided in a seat backframe 21 that forms the framework of the seat back 20, a seat pad 28 isdisposed on the front surface of the elastic installation supportingmembers 27, an airbag 30 in a contracted state is disposed rearwardly ofthe elastic installation supporting members 27, and all of thesecomponents are covered by an outer layer 31 in a bag shape.

The seat back frame 21 is formed in a substantially rectangular frameshape by a U-shaped tube frame, a pair of right and left side brackets24, a tube-shaped upper cross member 25, and a lower cross member 26,the U-shaped tube frame including an upper frame 22 extending in avehicle width direction and a pair of side frames 23 curving or bendingdownward from both ends of the upper frame 22 and extending downward,the pair of right and left side brackets 24 being fixedly disposed atthe side edges of the side frames 23, the tube-shaped upper cross member25 extending in a vehicle width direction and being installed betweenthe vicinities of the upper ends of the right and left side frames 23,the lower cross member 26 being installed between the vicinities of thelower ends of the right and left side brackets 24.

A plurality of the elastic installation supporting members 27 such aszigzag springs made of metal is provided to be bridged between theopposed side frames 23 and between the side brackets 24. In the presentimplementation, three elastic installation supporting members 27 areprovided to be bridged therebetween at substantially the same intervals.

The seat pad 28, which elastically supports the upper body Pb of theseated person Pf, is disposed on the front surface of the elasticinstallation supporting members 27, the seat pad being composed of aurethane foam material. The airbag 30, which is flatly folded in arectangular shape in a contracted state, is disposed in the rear of theelastic installation supporting members 27.

The whole thing including the seat back frame 21, the seat pad 28, andthe air bag 30 is covered by the outer layer 31 in a bag shape having afront surface 32 that covers the front of the seat pad 28 and a rearpart 33 that covers the air bag 30 with an expandable/contractible andflexible fabric (textile, knit, non-woven fabric) or leather (naturalleather, synthetic leather), thereby forming the seat back 20. A rearboard, which is a movable member, may be disposed at the rear portion.The air bag 30 is held in, for example, the outer layer 31 by aretaining unit (not illustrated) so as to allow inflation anddevelopment. The air bag 30 is provided with a gas inlet (notillustrated) and is connected to a cylindrical inflator 29 which isattached to a side surface 24 a outward of the side bracket 24 in thevehicle body.

The base end of each side bracket 24 included in the seat back frame 21of the seat back 20 is attached to a rotation arm 16 of a recliningdevice 15 disposed in the rear of the seat cushion 11 by screwing amounting bolt 17, and thus the seat back frame 21 is integrallyconnected to the rotation arm 16 of the reclining device 15. It is to benoted that existing publicly known reclining device 15 may be used,which is not directly related to the present disclosure and thusdetailed description is omitted.

As illustrated in FIGS. 1 and 2, a pair of right and left cylindricalstay brackets 42 is integrally formed with the upper frame 22 of theseat back frame 21. Stays 41 mounted in the headrest 40 are inserted inand retained to the stay brackets 42 via a headrest holder, and thus theheadrest 40 is mounted on the upper end of the seat back 20. Thus, asillustrated in FIGS. 1 and 2, the airbag 30 contracted in asubstantially rectangular plane shape is disposed between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 and thus is incorporated in the seat back 20. The seat back 20covers the front of the expandable and developable airbag 30 with theelastic installation supporting members 27 capable of elasticallysupporting rearward movement of the seated person Pf, and flexiblemembers such as the seat pad 28 and the front surface 32 of the outerlayer 31. On the other hand, the seat back 20 covers the rear of theairbag 30 with the rear part 33 of the outer layer 31 which a flexiblemember or a movable member capable of elastically receiving an impactforce which is applied to the rear of the seat back.

The airbag 30 is designed to instantly expand and developtwo-dimensionally due to expanded gas injection of the inflator 29. Theairbag 30 has orifices (not illustrated) that release internal gas tothe outside. The diameter and number of orifices are set so as to allowthe internal gas to be released gradually with the contraction of theairbag 30 after the inflation and development thereof.

This configuration ensures bending deformation of the elasticinstallation supporting members 27 and the seat pad 28 which areprovided within the seat back frame 21 disposed within the seat back 20,and thus elastic support of the seated person Pf in a normal seatingstate is appropriately obtained and favorable seating performance may beensured.

On the other hand, when the airbag 30 inflates and developstwo-dimensionally between the elastic installation supporting members 27and the rear part 33 of the outer layer 31 due to expanded gas injectionof the inflator 29, as illustrated in FIG. 3, the airbag 30 pushesforward and urges the elastic installation supporting members 27 and theseat pad 28 so as to allow the upper body Pb of the seated person Pf tobe elastically supported from the rear side, and the airbag 30 furtherdevelops and causes the rear part 33 of the outer layer 31 to expandrearwardly so as to allow an impact force applied to the rear part ofthe seat back 20 to be elastically received. The inflation anddevelopment of the airbag 30 is covered by the elastic installationsupporting members 27 that hold the airbag 30 and the rear part 33 ofthe outer layer 31 that extends and expands, and thus developmentbehavior and development pattern are controlled and stable inflation anddevelopment are maintained, and also sufficient volume of inflation anddevelopment is obtained, and the energy absorbing stroke of the airbag30 in a fore-and-aft direction of the vehicle body may be ensured.

FIG. 4 illustrates a control circuit of the vehicle seat airbag system.The control circuit includes a control unit 50 that controls inflationand development of the airbag 30, and the control unit 50 iselectrically connected to a collision detection sensor 51 and theinflator 29 to control the operation of the inflator 29 according tocollision occurrence information from the collision detection sensor 51and a program stored in a ROM 53, the collision detection sensor being acollision detection unit to detect a collision to the rear of a vehicle,that is, an impact of a rear-end collision.

The collision detection sensor 51 includes an acceleration sensor thatissues a signal according to acceleration which represents an impactforce at the time of a rear-end collision. The control unit 50determines whether or not a rear-end collision has occurred based oncomparison between acceleration detected by the collision detectionsensor 51 and a predetermined threshold value. Based on thedetermination of rear-end collision occurrence, the control portion 50operates the inflator 29 to cause the airbag 30 to expand and developwhen a rear-end collision has occurred.

The operation of the vehicle airbag system having the aboveconfiguration will be described.

In a vehicle equipped with the vehicle airbag system, when an impactgreater than or equal to a predetermined impact is applied to thevehicle due to a rear-end collision or the like, the impact is detectedby the collision detection sensor 51, and the control unit 50 outputs adrive signal to the inflator 29, which is ignited and expanded gas jetsfrom the inflator 29. In this manner, as illustrated in FIG. 3, theairbag 30 instantly inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31. Thus, rearward movement, due to a rear-end collision, of theupper body Pb of the seated person Pf on the front seat 10 iselastically received and regulated by the airbag 30 via the frontsurface 32 of the outer layer 31, the seat pad 28, and the elasticinstallation supporting members 27.

On the other hand, because of vehicle body deformation due to an impactand/or inertia due to a rear-end collision, the upper body of the seatedperson Pr on the rear seat 60 is moved rearward and pressed against theseat back, then is moved linearly forward by rebounding. Then, forexample, knees Pn come into contact with the rear part of the seat back20 of the front seat 10, and an impact force is applied to the rear partof the front seat 10. At this point, the knees Pn are elasticallyreceived by the airbag 30 which has expanded and developed between theelastic installation supporting members 27 and the rear part 33 of theouter layer 31 in the seat back 20, and thus forward movement areregulated, and the upper body Pb of the seated person Pf on the frontseat 10 avoids receiving an impact force from the knees Pn of the seatedperson Pr on the rear seat 60, and consequently the seated person Pf onthe front seat 10 is protected. Similarly, the knees Pn of the seatedperson Pr moving forward on the rear seat 60 are elastically receivedand protected by the airbag 30 which inflates and develops.

In the above description, when the collision detection sensor 51 detectsan impact greater than or equal to a predetermined impact, the controlunit 50 instantly operates and controls the inflator 29 to cause theairbag 30 to expand and develop. The control unit 50, however, maycontrol the airbag 30 so that the airbag 30 inflates and develops aftera predetermined time delay since the collision detection unit 51 detectsan impact. That is, the control unit 50 determines whether or not arear-end collision has occurred based on comparison between accelerationdetected by the collision detection sensor 51 and a predeterminedthreshold value, and operates the inflator 29 to cause the airbag 30 toexpand and develop after elapse of a predetermined time since a rear-endcollision occurred.

In this manner, the airbag 30 inflates and develops after elapse of apredetermined time since an occurrence of a rear-end collision, and soat an occurrence of a rear-end collision, the seat pad 28 of the seatback 20 and the elastic installation supporting members 27 undergobending deformation because of inertia, and the upper body Pb of theseated person Pf on the front seat 10 is moved rearward quickly to bepressed into the seat back 20. Then the head Ph is instantly restrainedand supported by the headrest 40 after the collision and thus a loadapplied to the neck is reduced. Subsequently, due to expanded gasinjection of the inflator 29, the airbag 30 inflates and developstwo-dimensionally between the elastic installation supporting members 27and the outer layer 31 that forms the rear part of the seat back 20,then the airbag 30 pushes forward and urges the elastic installationsupporting members 27 and the seat pad 28 so as to elastically supportthe upper body Pb of the seated person Pf, then develops and causes therear part 33 of the outer layer 31 to expand rearwardly so as to allowan impact force applied to the rear part of the seat back 20 to beelastically received. Accordingly, rearward movement, due to a rear-endcollision, of the upper body Pb of the seated person Pf on the frontseat 10 is elastically received and rearward movement is regulated bythe airbag 30 via the outer layer 31 of the seat back 20, the seat pad28, and the elastic installation supporting members 27, the airbag 30ensuring the amount of development and inflation, and the energyabsorbing stroke in a fore-and-aft direction of the vehicle body.

In this manner, similarly to what has been described above, the seatedperson Pf on the front seat 10 and the seated person Pr on the rear seat60 are protected by the airbag 30 which inflates and develops, and at anoccurrence of a rear-end collision, the upper body Pb of the seatedperson Pf on the front seat 10 is moved rearward quickly to be pressedinto the seat back 20, then the head Ph is supported by the headrest 40to reduce a load applied to the neck, and thus occurrence of whiplashinjury of the seated person Pf is reduced.

This vehicle seat airbag system may control its operation using acollision prediction unit instead of the above-mentioned controlcircuit.

FIG. 5 illustrates the control circuit of the vehicle seat airbagsystem. The control circuit includes a control unit 55 that controlsinflation and development of the airbag 30, and the control unit 55controls the operation of the inflator 29 according to collisionoccurrence information from the collision detection sensor 56 and aprogram stored in a ROM 57, the collision detection sensor being acollision prediction unit to predict a rear-end collision and an impactload to a vehicle.

Here, the control unit 55 has a built-in timer and measures time bystarting the timer from a rear-end collision predicted time. Also, thecollision detection sensor 56 includes, for example, a distance sensorsuch as a millimeter wave sensor, and predicts a rear-end collision bymeasuring a relative distance and/or a relative speed between theself-vehicle and another vehicle with which a rear-end collision mayoccur. In addition, the collision detection sensor 56 predicts an impactload at the occurrence of predicted rear-end collision.

In this manner, at a predicted occurrence time of collision, similarlyto what has been described above, as illustrated in FIG. 3, the airbag30 instantly inflates and develops between the elastic installationsupporting members 27 and the rear part 33 of the outer layer 31, andrearward movement of the upper body Pb of the seated person Pf on thefront seat 10 is elastically received and the rearward movement isregulated. On the other hand, even when the knees Pn of the seatedperson Pr on the rear seat 60 come into contact with the rear part ofthe seat back 20 of the front seat 10, the knees Pn are elasticallyreceived by the airbag 30 which has expanded and developed and rearwardmovement is regulated, and thus the seated person Pf on the front seat10 is protected.

In addition, when inevitability of a rear-end collision of a vehicle ispredicted based on signals from the collision detection sensor 56, thecontrol unit 55 may control the airbag 30 so that the airbag 30 startsto expand and develop after a predetermined time delay since thepredicted occurrence time of collision. That is, when the control unit55 predicts inevitability of a rear-end collision of the vehicle basedon signals from the collision detection sensor 56, inflation anddevelopment of the airbag 30 starts after elapse of a predetermined timesince the predicted occurrence time of collision.

In this manner, when a rear-end collision occurs at a predictedoccurrence time of collision, the seat pad 28 of the seat back 20 andthe elastic installation supporting members 27 undergo bendingdeformation because of the inertia of the seated person Pf, and theupper body Pb of the seated person Pf on the front seat 10 is movedrearward quickly to be pressed into the seat back 20, then the head Phis supported by the headrest 40 instantly after the collision. Theairbag 30 inflates and develops after elapse of a predetermined timesince a subsequent predicted occurrence time of collision. Thus,rearward movement, due to a rear-end collision, of the upper body Pb ofthe seated person Pf on the front seat 10 is elastically received by theairbag 30 via the outer layer 31 of the seat back 20, the seat pad 28,and the elastic installation supporting members 27, and so the rearwardmovement is regulated. In this manner, similarly to what has beendescribed above, the seated person Pf on the front seat 10 and theseated person Pr on the rear seat 60 are protected by the airbag 30which inflates and develops, and at an occurrence of a rear-endcollision, the upper body Pb of the seated person Pf on the front seat10 is moved rearward quickly to be pressed into the seat back 20, thenthe head Ph is supported by the headrest 40 to reduce a load applied tothe neck, and thus occurrence of whiplash injury of the seated person Pfis reduced.

Furthermore, when inevitability of a rear-end collision of a vehicle ispredicted based on signals from the collision detection sensor 56, thecontrol unit 55 may control the airbag 30 so that the airbag 30 startsto expand and develop a predetermined time delay before the predictedoccurrence time of collision. That is, when the control unit 55 predictsinevitability of a rear-end collision of the vehicle based on signalsfrom the collision detection sensor 56, inflation and development of theairbag 30 starts a predetermined time before the predicted occurrencetime of collision.

According to this, a predetermined time before a predicted occurrencetime of collision, that is before a collision occurrence, the airbag 30starts to expand and develop between the elastic installation supportingmembers 27 and the rear part 33 of the outer layer 31, the upper body Pbof the seated person Pf is pushed forward via the seat pad 28 and thefront surface 32 of the outer layer 31 by the airbag 30 which inflatesand develops, thereby causing the back of the seated person Pf to bestretched and the seated position and the seated posture of the seatedperson Pf is made to be suitable.

The airbag 30 further inflates and develops with the suitable seatedposition and seated posture of the seated person Pf, and thus optimaleffect of inflation and development of the airbag 30 for the seatedperson Pf is obtained, and rearward movement of the upper body Pb of theseated person Pf on the front seat 10 at an occurrence of a rear-endcollision is elastically received by the airbag 30 and the rearwardmovement is regulated.

Consequently, according to the present implementation, the airbag 30disposed within the seat back 20 inflates and develops within the seatback 20, thereby making it possible to elastically receive rearwardmovement of the seated person Pf due to a collision and to protect theseated person pf on the vehicle seat against an impact from the rear.Thus, without adopting a complicated configuration, direct protection ofa seated person by the airbag at the time of a collision and accuratereduction of an impact from the rear of the seat back may be achieved.

Moreover, because the inflator 29 is attached to the side surface 24 aoutward of the side bracket 24 of the seat back frame 21 in the vehiclebody, the seat back frame being a frame member disposed so as to ensureseating performance, and thus uncomfortable feeling for a seated personcaused by provision of the inflator 29 is completely insensible, and thesupport rigidity of the inflator 29 is ensured.

Furthermore, the inflator 29 is disposed outside the seat back frame 21,and thus interference between the inflator 29 and the airbag 30 whichinflates and develops within the seat back 20 is completely avoided, andthus stable development of the airbag 30 is ensured.

Also, when the front seat 10 is provided with a side air bag, theinflator 29 may be used in common as an inflator of the side air bag,and the efficiency of the entire air bag device provided in the frontseat 10 may be increased.

When a lumbar support mechanism is provided within the seat back frame21 of the front seat 10, the operation of the lumbar support mechanismis not effected.

According to this implementation, the inflator 29 is not located betweenthe opposed side brackets 24 or between the opposed side frames 23,thereby providing the effect that attachment of the elastic installationsupporting members 27 to be installed between the side brackets 24 orthe side frames 23 is not interfered.

As described above, the operation of the airbag 30 at an occurrence ofcollision to the front seat 10 has been described by taking a rear-endcollision of a vehicle as an example. However, a collision is notlimited to a rear-end collision. For example, even in the case of afront-end collision, although operational steps are reversed, similarly,the inflation and development of the airbag 30 first allows the frontseat 10 to elastically receive an impact due to forward movement of theknees Pn of the seated person Pr on the rear seat, and subsequently, thefront seat 10 is able to elastically receive rearward movement of theupper body Pb of the seated person Pf on the front seat 10.

Second Implementation

A second implementation will be described with reference to FIGS. 6 to17. FIG. 6 is a schematic explanatory diagram as seen from the rear,illustrating the outline of the second implementation; FIG. 7 is anoperation explanatory diagram of the vehicle seat when an impact occurs;and FIG. 8 is an operation explanatory diagram of the vehicle seat. Itis to be noted that the components corresponding to those in the firstimplementation are denoted by the same symbols in FIGS. 1 to 5, anddetailed description of the components is omitted.

Similarly to the first implementation, in a front seat 10, a pluralityof elastic installation supporting members 27 is provided in a seat backframe 21 that forms a framework of a seat back 20, a seat pad 28 isdisposed on the front surface of the elastic installation supportingmembers 27, an airbag 30 in a contracted state is disposed rearwardly ofthe elastic installation supporting members 27, and all of thesecomponents are covered by an outer layer 31 in a bag shape.

As illustrated in FIG. 6, in a rear part 33 of the outer layer 31, asubstantially rectangular airbag corresponding area 74A, whichcorresponds to the airbag 30, is composed of an outer layer materialwhich is superior in elasticity compared with the outer layer materialof a rear part area 74B which surrounds the airbag corresponding area74A. Thus, an elastic portion is formed correspondingly to the airbag30.

On the other hand, when the airbag 30 inflates and developstwo-dimensionally between the elastic installation supporting members 27and the rear part 33 of the outer layer 31 due to expanded gas injectionof the inflator 29, as illustrated in the cross-sectional view of FIG. 7and in the main perspective view of the rear part 33 of FIG. 8, theairbag 30 pushes forward and urges the elastic installation supportingmembers 27 and the seat pad 28 so as to allow the upper body Pb of theseated person Pf to be elastically supported from the rear side. On theother hand, in the rear part 33 of the outer layer 31, particularly thearea 74A corresponding to the airbag 30 expands rearwardly in arectangular dome-shaped, the volume of inflation and development of theairbag 30 is sufficiently ensured, and the airbag 30 develops to allowan impact force applied to the rear part of the seat back 20 to beelastically received, the airbag being composed of an outer layermaterial superior in elasticity.

The inflation and development of the airbag 30 is covered by the elasticinstallation supporting members 27 that hold the airbag 30 and the rearpart 33 of the outer layer 31 that extends and expands, and thusdevelopment behavior and development pattern are controlled and stableinflation and development are maintained. In addition, theexpandable/contractible elastic installation supporting members 27 andthe rear part 33 of the outer layer 31 are caused to expand, inflate anddevelop, thereby making it possible to obtain the volume of inflationand development of the airbag 30, and the energy absorbing stroke in afore-and-aft direction of the vehicle body in the airbag 30 may beensured.

In a vehicle provided with vehicle seats having the above configuration,when an impact greater than or equal to a predetermined impact isapplied to the vehicle due to a rear-end collision or the like, theimpact is detected by the collision detection sensor, and the controlunit outputs a drive signal to the inflator 29, which is ignited andexpanded gas jets from the inflator 29. In this manner, as illustratedin FIGS. 7 and 8, the airbag 30 instantly inflates and develops betweenthe elastic installation supporting members 27 and the rear part 33 ofthe outer layer 31. Thus, rearward movement, due to a rear-endcollision, of the upper body Pb of the seated person Pf on the frontseat 10 is elastically received by the airbag 30 via the front surface32 of the outer layer 31, the seat pad 28, and the elastic installationsupporting members 27, and so the rearward movement is regulated.

On the other hand, the seated person Pr on the rear seat 60 may be movedrearward due to a rear-end collision and pressed against the seat back,then is moved linearly forward by rebounding. Then, for example, theknees Pn may come into contact with the rear part of the seat back 20 ofthe front seat 10. At this point, the knees Pn are elastically receivedvia the outer layer 31 which inflates and develops by the airbag 30which has expanded and developed between the elastic installationsupporting members 27 and the rear part 33 of the outer layer 31 in theseat back 20, and thus forward movement is restrained and the upper bodyPb of the seated person Pf on the front seat 10 is protected against animpact force F1 from the knees Pn of the seated person Pr on the rearseat 60. Similarly, the impact force F1 from the knees Pn and an impactforce F2 from the upper body of the seated person Pr moving forward onthe rear seat 60 are elastically received and protected by the airbag 30which has expanded and developed and ensures the volume of inflation anddevelopment and the energy absorbing stroke.

In the rear part 33 which is of the outer layer 31 of the seat back 20and expands along with the inflation and development of the airbag 30,as illustrated in FIG. 9A, a rear part area 81B, which surrounds asubstantially rectangular airbag corresponding area 81A, may be composedof an outer layer material which is superior in elasticity compared withthe outer layer material of the airbag corresponding area 81Acorresponding to the airbag 30. Thus, an elastic portion may be formedin the rear part area 81B surrounding the airbag corresponding area 81A.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 due to a rear-end collision or the like. As illustrated in FIG.9B, the airbag 30 inflates and develops so as to expand due to extensionof the rear part area 81B which surrounds the airbag corresponding area81A included in the rear part 33. Thus, rearward movement, due to arear-end collision, of the upper body Pb of the seated person Pf on thefront seat 10 is elastically received by the airbag 30 and the rearwardmovement is regulated.

On the other hand, the knees Pn of the seated person Pr on the rear seat60 is elastically received by the airbag 30 which has expanded anddeveloped between the elastic installation supporting members 27 and theouter layer 31, and thus the upper body Pb of the seated person Pf onthe front seat 10 is protected against the impact force F1. Similarly,the impact force F1 from the knees Pn and the impact force F2 from theupper body of the seated person Pr moving forward on the rear seat 60are elastically received and protected by the airbag 30 which hasexpanded and developed.

The inflation and development of the airbag 30 are controlled by theelastic installation supporting members 27 and mainly the rear part 33of the outer layer 31, that expands due to extension of the rear partarea 81B surrounding the airbag corresponding area 81A, and thus stableinflation and development are maintained.

Another rear part 33, which is of the outer layer 31 of the seat back 20and expands along with the inflation and development of the airbag 30,has an airbag corresponding area 82A corresponding to the airbag 30 ofthe rear part 33 and a rear part area 82B surrounding the airbagcorresponding area 82A as illustrated in FIG. 10A, the airbagcorresponding area 82A being defined as a substantially U-shape alongboth side edges 82 b and a lower edge 82 c, the rear part area 82Bhaving both side edges 82 e and a lower edge 82 f, the both side edges82 e being gradually away from the both side edges 82 b as being locateddownward from the upper end of each side edge 82 b, the lower edge 82 fextending from the lower edge 82 c with a predetermined distance apartand having both ends connected with the lower ends of the both sideedges 82 e. The airbag corresponding area 82A is formed in a lid shapehaving an upper edge 82 a which is connected with the rear part area82B.

A pair of elastic side areas 82C and a strip-shaped lower elastic area82D are integrally formed, the elastic side areas 82C being formed byplacing a substantially upwardly tapered outer layer material superiorin elasticity between the both side edges 82 b of the airbagcorresponding area 82A and the both side edges 82 e of the rear partarea 82B and by seaming the outer layer material and corresponding bothside edges together, the lower elastic area 82D being formed by placingthe outer layer material between the lower edge 82 c of the airbagcorresponding area 82A and the lower edge 82 f of the rear part area 82Band by seaming the outer layer material and corresponding lower edgestogether.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 due to a rear-end collision or the like. As illustrated in FIG.10B, when the airbag corresponding area 82A included in the rear part 33is pressed, the elastic both side areas 82C and the lower elastic area82D having superior elasticity extend, and the lower edge 82 c protrudessignificantly rearward with respect to the upper edge 82 a of thelid-shaped airbag corresponding area 82A, and thus the volume ofinflation and development is ensured and the airbag 30 develops in asubstantially triangular cross-sectional shape with which the energyabsorbing stroke in a fore-and-aft direction of the vehicle body may beensured.

The inflation and development of the airbag 30 are controlled and stableinflation and development are maintained by the elastic installationsupporting members 27 and mainly the rear part 33 of the outer layer 31,that expands by the rear part area 82B surrounding the airbagcorresponding area 82A and the expandable elastic both side areas 82Cand lower elastic area 82D. Thus, rearward movement, due to a rear-endcollision, of the upper body Pb of the seated person Pf on the frontseat 10 is elastically received by the airbag 30 and the rearwardmovement is restrained.

On the other hand, diagonally upwardly pushed knees Pn of the seatedperson Pr on the rear seat 60 are elastically received effectively bythe lower portion of the airbag 30 which has significantly expanded anddeveloped between the elastic installation supporting members 27 and theouter layer 31 in the seat back 20, and thus forward movement isrestrained and the upper body Pb of the seated person Pf on the frontseat 10 avoids receiving the impact force F1 from the knees Pn of theseated person Pr on the rear seat 60. Similarly, the impact force F1from the knees and the impact force F2 from the upper body of the seatedperson Pr moving forward on the rear seat 60 are elastically receivedand protected by the airbag 30 which inflates, develops and expands.

Another rear part 33, which is of the outer layer 31 of the seat back 20and expands along with the inflation and development of the airbag 30,has an airbag corresponding area 83A corresponding to the airbag 30 ofthe rear part 33 and a rear part area 83B surrounding the airbagcorresponding area 83A as illustrated in FIG. 11A, the airbagcorresponding area 83A being defined as a substantially U-shape alongboth side edges 83 b and a upper edge 83 a, the rear part area 83Bhaving both side edges 83 e and a upper edge 83 g, the both side edges83 e being gradually away from the both side edges 83 b as being locateddownward from the lower end of each side edge 83 b, the upper edge 83 gextending from the upper edge 83 a with a predetermined distance apartand having both ends connected with the upper ends of the both sideedges 83 e. The airbag corresponding area 83A is formed in asubstantially rectangular lid shape having an lower edge 83 c which isconnected with the rear part area 83B.

A pair of elastic side areas 83C and a strip-shaped upper elastic area83D are integrally formed, the elastic side areas 83C being formed byplacing a substantially downwardly tapered outer layer material superiorin elasticity between the both side edges 83 b of the airbagcorresponding area 83A and the both side edges 83 e of the rear partarea 83B and by seaming the outer layer material and corresponding bothside edges together, the upper elastic area 83D being formed by placingthe outer layer material between the upper edge 83 a of the airbagcorresponding area 83A and the upper edge 83 g of the rear part area 83Band by seaming the outer layer material and corresponding upper edgestogether.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the outer layer 31 due to arear-end collision or the like. As illustrated in FIG. 11B, when theairbag corresponding area 83A is pressed from the inner side of the seatback including the rear part 33, the elastic both side areas 83C and theupper elastic area 83D having superior elasticity extend, and the airbag30 inflates and develops in a substantially triangular cross-sectionalshape in which the upper edge 83 a protrudes significantly rearward withrespect to the lower edge 83 c of the lid-shaped airbag correspondingarea 83A.

The inflation and development of the airbag 30 are controlled and stableinflation and development are maintained by the elastic installationsupporting members 27 and mainly the rear part 33 of the outer layer 31,that expands by the rear part area 83B surrounding the airbagcorresponding area 83A and the expandable elastic both side areas 83Cand upper elastic area 83D. Thus, rearward movement, due to a rear-endcollision, of the upper body Pb of the seated person Pf on the frontseat 10 is elastically received by the airbag 30 and the rearwardmovement is regulated.

On the other hand, diagonally upwardly pushed knees Pn of the seatedperson Pr on the rear seat 60 are elastically received effectively bythe lower portion of the airbag 30 which has expanded and developed tobe inclined between the elastic installation supporting members 27 andthe outer layer 31 in the seat back 20, and the upper body iselastically received effectively by the upper portion of the airbag 30which inflates and develops significantly. The upper body Pb of theseated person Pf on the front seat 10 is protected against the impactforce F1 from the knees Pn of the seated person Pr on the rear seat 60.Similarly, the impact force F1 from the knees Pn and the impact force F2from the upper body of the seated person Pr moving forward on the rearseat 60 are elastically received and protected by the airbag 30 whichinflates.

As illustrated in FIG. 12A, another rear part 33, which is of the outerlayer 31 of the seat back 20 and expands along with the inflation anddevelopment of the airbag 30, has an upper airbag corresponding area 84Aand a lower airbag corresponding area 84B that correspond to the airbag30 of the rear part 33, and a rear part area 84C, the upper and lowerairbag corresponding areas 84A, 84B having both side edges 84 bseparated above and below and a lower edge 84Ac and an upper edge 84Baseparated across a central portion, a rear part area 84C surrounding theupper airbag corresponding area 84A and the lower airbag correspondingarea 84B, the rear part area 84C having side edges 84 e each beinggradually away from the corresponding side edge 84 b as being locatednear the center in a height direction from the lower end and the upperend of the side edge 84 b. The upper airbag corresponding area 84A andthe lower airbag corresponding area 84B is formed in a substantiallyrectangular lid shape having an upper edge 84Aa and a lower edge 84Bcwhich are connected with the rear part area 84C, the lower edge 84Ac andthe upper edge 84Ba facing each other with a space.

A pair of elastic side areas 84D and an elastic central area 84E areintegrally formed, the elastic side areas 84D being formed by placing anouter layer material superior in elasticity between the side edges 84 bof the upper and lower airbag corresponding areas 84A, 84B and the sideedges 84 e of the rear part area 84C and by seaming the side edges 84 band the side edges 84 e together, the elastic central area 84E beingformed by placing a strip-shaped outer layer material superior inelasticity between the lower edge 84Ac of the upper airbag correspondingarea 84A and the upper edge 84Ba of the lower airbag corresponding area84B and by seaming the lower edge 84Ac and the upper edge 84Ba together.Consequently, the inflation and development of the airbag 30 arecontrolled and stable inflation and development are maintained by theelastic installation supporting members 27, and mainly the rear partarea 84C surrounding the upper airbag corresponding area 84A and thelower airbag corresponding area 84B, and the rear part 33 of the outerlayer 31, that expands by the expandable elastic side areas 84D andelastic central area 84E.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 due to a rear-end collision or the like. As illustrated in FIG.12B, when the upper airbag corresponding area 84A and the lower airbagcorresponding area 84B are pressed from the inner side of the seat backincluding the rear part 33, the elastic side areas 84D and the elasticcentral area 84E having superior elasticity extend, and the airbag 30inflates and develops in a substantially trapezoidal cross-sectionalshape in which the lower edge 84Ac protrudes rearwardly with respect tothe upper edge 84Aa of the lid-shaped upper airbag corresponding area84A, the upper edge 84Ba protrudes rearwardly with respect to the loweredge 84Bc of the lower airbag corresponding area 84B, and the upperairbag corresponding area 84A and the lower airbag corresponding area84B are inclined. Thus, rearward movement, due to a rear-end collision,of the upper body Pb of the seated person Pf on the front seat 10 iselastically received by the airbag 30 and the rearward movement isregulated.

On the other hand, diagonally upwardly pushed knees Pn of the seatedperson Pr on the rear seat 60 are elastically received effectively bythe lower portion of the airbag 30 which has expanded and developed tobe inclined, and the upper body is elastically received effectively bythe upper portion of the airbag 30 which inflates and develops, andforward movement is restrained, and thus the upper body Pb of the seatedperson Pf on the front seat 10 avoids receiving the impact force F1 fromthe knees of the seated person Pr on the rear seat 60. Similarly, theimpact force F1 from the knees Pn and the impact force F2 from the upperbody of the seated person Pr moving forward on the rear seat 60 areelastically received and protected by the airbag 30 which inflates,develops and expands.

The inflation and development of the airbag 30 are controlled and stableinflation and development are maintained by the elastic installationsupporting members 27, and mainly the rear part area 84C surrounding theupper airbag corresponding area 84A and the lower airbag correspondingarea 84B, and the rear part 33 of the outer layer 31, that expands bythe expandable elastic side areas 84D and elastic central area 84E.

Another rear part 33, which is of the outer layer 31 of the seat back 20and expands along with the inflation and development of the airbag 30,has an airbag corresponding area 85A corresponding to the airbag 30 ofthe rear part 33 and a rear part area 85B surrounding the airbagcorresponding area 85A as illustrated in FIG. 13A, the airbagcorresponding area 85A being defined as a substantially U-shape alongboth side edges 85 b and a lower edge 85 c, the rear part area 85Bhaving both side edges 85 e and a lower edge 85 f along the side edges85 b and the lower edge 85 c of the airbag corresponding area 85A. Theairbag corresponding area 85A is formed in a substantially rectangularlid shape having an upper edge 85 a which is connected with the rearpart area 85B.

A gusset 85C folded in an upward tapered shape is placed between eachside edge 85 b of the airbag corresponding area 85A and a correspondingside edge 85 e of the rear part area 85B, and the gusset and the sideedges are seamed together. Similarly, a gusset 85D folded in a stripform is placed between the lower edge 85 c of the airbag correspondingarea 85A and the lower edge 85 f of the rear part area 85B, and thegusset and the lower edges are seamed together. Furthermore, the sideedges 85 b and the lower edge 85 c of the airbag corresponding area 85A,and the side edge 85 e and the lower edge 85 f of the rear part area 85Bare seamed together by a relatively fragile seam thread (notillustrated) with the corresponding edges overlapped or in contact witheach other, the seam thread being breakable by the inflation anddevelopment of the airbag 30.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 due to a rear-end collision or the like. As illustrated in FIG.13B, when the airbag corresponding area 85A included in the rear part 33is pressed, the pressure causes the seam thread to be broken, the seamthread being used for seaming the side edges 85 b and the lower edge 85c of the airbag corresponding area 85A, and the side edge 85 e and thelower edge 85 f of the rear part area 85B together. Thus, the gusset 85Cand the gusset 85D extend and develop, and the airbag 30 inflates anddevelops in a substantially triangular cross-sectional shape in whichthe volume of inflation and development is ensured such that the loweredge 85 c protrudes significantly rearward with respect to the upperedge 85 a of the lid-shaped airbag corresponding area 85A.

In the inflation and development of the airbag 30, development behaviorand development pattern are controlled and stable inflation anddevelopment pattern are maintained by the elastic installationsupporting members 27, and mainly the rear part area 85B surrounding theairbag corresponding area 85A, and the expandable gusset 85C and gusset85D. Thus, rearward movement, due to a rear-end collision, of the upperbody Pb of the seated person Pf on the front seat 10 is elasticallyreceived by the airbag 30 and the rearward movement is regulated.

On the other hand, diagonally upwardly pushed knees Pn of the seatedperson Pr on the rear seat 60 are elastically received effectively bythe lower portion of the airbag 30 which has significantly expanded anddeveloped, and thus forward movement is restrained and the seated personPf on the front seat 10 avoids receiving the impact force F1 from theknees Pn of the seated person Pr on the rear seat 60. Similarly, theimpact force F1 from the knees Pn and the impact force F2 from the upperbody of the seated person Pr moving forward on the rear seat 60 areelastically received and protected by the airbag 30 which inflates,develops and expands.

Another rear part 33, which is of the outer layer 31 of the seat back 20and expands along with the inflation and development of the airbag 30,has an airbag corresponding area 86A corresponding to the airbag 30 ofthe rear part 33 and a rear part area 86B surrounding the airbagcorresponding area 86A as illustrated in FIG. 14A, the airbagcorresponding area 86A being defined as a substantially U-shape alongboth side edges 86 b and an upper edge 86 a, the rear part area 86Bhaving both side edges 86 e and an upper edge 86 d along the side edges86 b and the upper edge 86 a of the airbag corresponding area 86A. Theairbag corresponding area 86A is formed in a substantially rectangularlid shape having a lower edge 86 c which is connected with the rear partarea 86B.

A gusset 86C folded in a downward tapered shape is placed between eachside edge 86 b of the airbag corresponding area 86A and thecorresponding side edge 86 e of the rear part area 86B, and the gussetand the side edges are seamed together. Similarly, a gusset 86D foldedin a strip form is placed between the upper edge 86 a of the airbagcorresponding area 86A and the upper edge 86 d of the rear part area86B, and the gusset and the lower edges are seamed together.Furthermore, the side edges 86 b and the upper edge 86 a of the airbagcorresponding area 86A, and the side edge 86 e and the lower edge 86 dof the rear part area 86B are seamed together by a relatively fragileseam thread with the corresponding edges overlapped or in contact witheach other, the seam thread being breakable by the inflation anddevelopment of the airbag 30.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 due to a rear-end collision or the like. As illustrated in FIG.14B, when the airbag corresponding area 86A included in the rear part 33is pressed, the pressure causes the seam thread to be broken, the seamthread being used for seaming the side edges 86 b and the upper edge 86a of the airbag corresponding area 86A, and the side edge 86 e and theupper edge 86 d of the rear part area 86B together. Thus, the gusset 86Cand the gusset 86D extend and develop, and the airbag 30 inflates anddevelops in a substantially triangular cross-sectional shape in whichthe volume of inflation and development and the energy absorbing strokeare ensured such that the upper edge 86 a protrudes significantlyrearward with respect to the lower edge 86 c of the lid-shaped airbagcorresponding area 86A. Thus, rearward movement, due to a rear-endcollision, of the upper body Pb of the seated person Pf on the frontseat 10 is elastically received by the airbag 30 and is regulated.

On the other hand, the seated person Pr on the rear seat 60 iselastically received effectively by the lower portion of the airbag 30which has significantly expanded and developed, and thus forwardmovement is restrained and the seated person Pf on the front seat 10avoids receiving the impact force F1 from the knees Pn of the seatedperson Pr on the rear seat 60. Similarly, the impact force F1 from theknees Pn and the impact force F2 due to contact of the upper body of theseated person Pr moving forward on the rear seat 60 are elasticallyreceived and protected by the airbag 30 which inflates, develops andexpands.

Another rear part 33, which is of the outer layer 31 of the seat back 20and expands along with the inflation and development of the airbag 30,has an airbag corresponding area 87A corresponding to the airbag 30 ofthe rear part 33 and a rear part area 87B surrounding the airbagcorresponding area 87A as illustrated in FIG. 15A, the airbagcorresponding area 87A being partitioned by a fragile portion 87 d whichis a substantially U-shape along both side edges 87 b and a lower edge87 c and which serves as a rupture portion which is breakable by theinflation and development of the airbag 30. The airbag correspondingarea 87A is formed in a substantially rectangular lid shape having anupper edge 87 a which is connected with the rear part area 87B.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 due to a rear-end collision or the like. As illustrated in FIG.15B, when the airbag corresponding area 87A included in the rear part 33is pressed, the pressure causes the fragile portion 87 d to be graduallyruptured and opened from below, and the airbag 30 inflates and developsin a substantially triangular cross-sectional shape in which the volumeof inflation and development and the energy absorbing stroke are ensuredsuch that the lower edge 87 c of the airbag corresponding area 87Aprotrudes significantly rearward, the fragile portion 87 d being formedalong the area from the lower edge 87 c to the both side edges 87 b.

The inflation and development of the airbag 30 are controlled and thusstable inflation and development are maintained by the elasticinstallation supporting members 27 and the rear part area 87Bsurrounding the airbag corresponding area 87A which is ruptured in thefragile portion 87 d along with the inflation and development of theairbag 30. Thus, rearward movement, due to a rear-end collision, of theupper body Pb of the seated person Pf on the front seat 10 iselastically received by the airbag 30 and the rearward movement isregulated.

On the other hand, diagonally upwardly pushed knees Pn of the seatedperson Pr on the rear seat 60 are elastically received effectively bythe lower portion of the airbag 30 which has expanded and developed, andthus forward movement is restrained and the upper body Pb of the seatedperson Pf on the front seat 10 avoids receiving the impact force F1 fromthe knees Pn of the seated person Pr on the rear seat 60. Similarly, theimpact force F1 due to contact of the knees and the impact force F2 dueto contact of the upper body of the seated person Pr on the rear seat 60are elastically received and protected by the airbag 30 which inflates,develops and expands.

Another rear part 33, which is of the outer layer 31 of the seat back 20and expands along with the inflation and development of the airbag 30,has an airbag corresponding area 88A corresponding to the airbag 30 ofthe rear part 33 and a rear part area 88B surrounding the airbagcorresponding area 88A as illustrated in FIG. 16A, the airbagcorresponding area 88A being partitioned by a fragile portion 88 d whichis a substantially U-shape along both side edges 88 b and an upper edge88 a and which serves as a rupture portion which is breakable by theinflation and development of the airbag 30. The airbag correspondingarea 88A is formed in a substantially rectangular lid shape having alower edge 88 c which is connected with the rear part area 88B.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 due to a rear-end collision or the like. As illustrated in FIG.16B, when the airbag corresponding area 88A included in the rear part 33is pressed, the pressure causes the fragile portion 88 d to be graduallyruptured and opened from above, and the airbag 30 inflates and developsin a substantially triangular cross-sectional shape in which the volumeof inflation and development and the energy absorbing stroke are ensuredsuch that the upper edge 88 a of the airbag corresponding area 88Aprotrudes significantly rearward, the fragile portion 88 d being formedalong the area from the upper edge 88 c to the both side edges 88 b.

The inflation and development of the airbag 30 are controlled and stableinflation and development are maintained by the elastic installationsupporting members 27 and the rear part area 88B surrounding the airbagcorresponding area 88A which is divided via the fragile portion 88 dthat is ruptured along with the inflation and development of the airbag30. Thus, rearward movement, due to a rear-end collision, of the upperbody Pb of the seated person Pf on the front seat 10 is elasticallyreceived by the airbag 30 and the rearward movement is regulated.

On the other hand, diagonally upwardly pushed knees Pn of the seatedperson Pr on the rear seat 60 are elastically received by the lowerportion of the airbag 30 and forward movement is restrained, whereas theupper body such as the chest is elastically received by the upperportion of the airbag 30 which has significantly expanded and developed,and forward movement is restrained.

In this manner, the upper body Pb of the seated person Pf on the frontseat 10 avoids receiving the impact force F1 from the knees Pn of theseated person Pr on the rear seat 60. Similarly, the impact force F1 dueto contact of the knees and the impact force F2 from the upper body ofthe seated person Pr moving forward on the rear seat 60 are elasticallyreceived and protected by the airbag 30 which inflates, develops andexpands.

Another rear part 33, which is of the outer layer 31 of the seat back 20and expands along with the inflation and development of the airbag 30,has an upper airbag corresponding area 89A and a lower airbagcorresponding area 89B that correspond to the airbag 30 of the rear part33, and a rear part area 89C surrounding the upper airbag correspondingarea 89A and the lower airbag corresponding area 89B, the upper airbagcorresponding area 89A, the lower airbag corresponding area 89B, and therear part area 89C being partitioned in a substantially H-shape byfragile portions 89 c, 89 d which are breakable by the inflation anddevelopment of the airbag 30, the substantially H-shape extending in awidth direction at the center of both side edges 89 b, 89 b in a heightdirection. A lower edge 89Ac of the upper airbag corresponding area 89Aand an upper edge 89Ba of the lower airbag corresponding area 89B areconnected via the fragile portion 89. The upper airbag correspondingarea 89A and the lower airbag corresponding area 89B are formed in asubstantially rectangular lid shape respectively having an upper edge89Aa and a lower edge 89Bc which are connected with the rear part area89C.

In this manner, the airbag 30 inflates and develops between the elasticinstallation supporting members 27 and the rear part 33 of the outerlayer 31 due to a rear-end collision or the like. As illustrated in FIG.17B, when the upper airbag corresponding area 89A and the lower airbagcorresponding area 89B forming the rear part 33 are pressed, thepressure causes the fragile portion 89 d and the fragile portions 89 cto be gradually ruptured, the fragile portion 89 d being between theupper airbag corresponding area 89A and the lower airbag correspondingarea 89B, the fragile portions 89 c being formed along the both sideedges 89 b. Then the space between the lower edge 89Ac of the upperairbag corresponding area 89A and the upper edge 89Ba of the lowerairbag corresponding area 89B starts to be opened, and the airbag 30inflates and develops in a substantially trapezoidal or triangular shapein which the volume of inflation and development and the energyabsorbing stroke are available such that the lower edge 89Ac of theupper airbag corresponding area 89A and the upper edge 89Ba of the lowerairbag corresponding area 89B at the center in a height directionprotrude significantly rearward.

The inflation and development of the airbag 30 are controlled and stableinflation and development are maintained by the elastic installationsupporting members 27, the upper airbag corresponding area 89A, thelower airbag corresponding area 89B, and the rear part area 89Csurrounding the upper airbag corresponding area 89A and the lower airbagcorresponding area 89B, the upper airbag corresponding area 89A and thelower airbag corresponding area 89B being ruptured in the fragileportions 89 d, 89 c along with the inflation and development of theairbag 30. Thus, rearward movement, due to a rear-end collision, of theupper body Pb of the seated person Pf on the front seat 10 iselastically received by the airbag 30 and the rearward movement isrestrained.

On the other hand, diagonally upwardly pushed knees Pn of the seatedperson Pr on the rear seat 60 are elastically received by the lowerportion of the airbag 30 which has expanded and developed between theelastic installation supporting members 27 and the rear part 33 of theouter layer 31 in the seat back 20, and forward movement is restrained,whereas the upper body such as the chest is elastically received by theupper portion of the airbag 30 which has significantly expanded anddeveloped, and forward movement is restrained.

In this manner, the upper body Pb of the seated person Pf on the frontseat 10 avoids receiving the impact force F1 from the knees Pn of theseated person Pr on the rear seat 60, and the seated person Pf on thefront seat 10 is protected. Similarly, the impact force F1 from theknees and the impact force F2 from the upper body of the seated personPr moving forward on the rear seat 60 are elastically received andprotected by the airbag 30 which inflates, develops and expands.

In each of the above-described implementations, the rear board may bedisposed along an expansion area which is formed in the rear part of theouter layer 31, and thus disposition of the rear board has no effect onthe expansion deformation of the expansion area.

Thus, according to the above-described implementations, the simpleconfiguration, in which the airbag disposed within the seat back causesthe outer layer to expand rearward within the seat back, ensures thevolume of inflation and development and the energy absorbing stroke ofthe airbag, thereby making it possible to elastically receive rearwardmovement of a seated person due to a collision and to protect the seatedperson against an impact from the rear. Consequently, without adopting acomplicated configuration, direct protection of a seated person by theairbag at the time of a collision and accurate reduction of an impactfrom the rear of the seat back may be achieved.

Third Implementation

A third implementation will be described with reference to FIGS. 18 to22. FIG. 18 is a vertical cross-sectional view illustrating the outlineof a vehicle seat; FIG. 19 is a schematic perspective view with partialcutaway of the vehicle seat as seen from the rear; FIG. 20A is anenlarged view of portion a of FIG. 18 illustrating the outline of a rearboard supporter; FIG. 20B is an enlarged view of portion b of FIG. 18illustrating the outline of a rear board retainer; and FIG. 21 is anoperation explanatory diagram of the vehicle seat when an impact occurs.It is to be noted that the components corresponding to those in thefirst implementation are denoted by the same symbols and detaileddescription of the components is omitted.

As illustrated in FIGS. 18 and 19, in the front seat 10, a plurality ofelastic installation supporting members 27 is provided in the seat backframe 21 that forms the framework of the seat back 20, the seat pad 28is disposed on the front surface of the elastic installation supportingmembers 27, the airbag 30 in a contracted state is disposed between theelastic installation supporting members 27 and a rear board 90, and theentire components except for the rear board 90 are covered by the outerlayer 31 in a bag shape.

The seat pad 28, which elastically supports the upper body Pb of theseated person Pf from the rear part side, is disposed on the frontsurface of the elastic installation supporting members 27, the seat padbeing composed of a urethane foam material. The airbag 30, which isflatly folded in a rectangular shape in a contracted state, is disposedbetween the elastic installation supporting members 27 and the rearboard 90.

The rear board 90 is in a substantially rectangular shape and covers therear part of the seat back 20 in the rear of the airbag 30. The upperportion and the lower portion of the rear board 90 are attached to theseat back frame 21 by a rear board supporter 91 and a rear boardretainer 92, respectively. It is to be noted that the rear board 90 ismade of a hard resin and includes a plurality of fragile portions 90 athat are each formed as a groove or a thin layer to achievepredetermined bending deformation. Also, due to the formation of thefragile portions 90 a, when an excessive load is applied to the rearboard 90, the rear board 90 bends along the fragile portions 90 a or areruptured along the fragile portions 90 a and thus fracture ofunspecified portions is prevented and at the time of fracture,occurrence of sharp protrusions on a fracture surface, that is,occurrence of sharp edges may be avoided.

As illustrated in FIGS. 18 and 20A, the rear board supporter 91 includesa supporting bracket 91A, a bracket 91B, and a hinge mechanism 91C, thesupporting bracket being connected to the upper end rear face of theright and left side brackets 24 and protruding rearward, the bracketbeing connected to the upper both ends of the rear board 90 andprotruding forward, the hinge mechanism connecting the supportingbracket and bracket in a swingable manner. In this manner, the upperportion of the rear board 90 is supported by the upper portion of theseat back frame 21 via the hinge mechanism 91C as a fulcrum in aforwardly and rearwardly swingable manner.

As illustrated in FIGS. 18 and 20B, the rear board retainer 92 is ahat-like shape which is attached to the lower end rear face of each sidebracket 24, and includes a retaining bracket 92A, a clip holder 92B, anda clip 92C, the retaining bracket including a clip retaining hole 92 aon a portion of the rear board 90 in a protruding manner, the clip beingmounted and supported on the end of the clip holder. The clip 92Cmounted and supported on the clip retainer 92B is inserted and retainedin the clip retaining hole 92 a of the retaining bracket 92A provided inthe side bracket 24, thereby fixing the rear board 90 at a normal useposition illustrated in FIG. 18.

On the other hand, when a load greater than or equal to a predeterminedvalue is applied to the front surface of the rear board 90 from thefront, as illustrated in FIGS. 18 and 20B by a virtual line, along withrearward movement of the rear board 90, the clip 92C mounted andsupported on the clip retainer 92B is removed from the clip retaininghole 92 a of the retaining bracket 92A and the fixing is released.

On the other hand, when the airbag 30 inflates and develops between theelastic installation supporting members 27 and the rear board 90 due toexpanded gas injection of the inflator 29, as illustrated in FIG. 21,the airbag 30 pushes forward and urges the elastic installationsupporting members 27 and the seat pad 28 so as to allow the upper bodyPb of the seated person Pf to be elastically supported from the rearside, and the airbag 30 also pushes the rear board 90 rearward to removethe clip 92C mounted and supported on the clip retainer 92B from theclip retaining hole 92 a of the retaining bracket 92A, and thus thefixing is released. In addition, the rear board 90 is moved rearward,that is, the rear board 90 is swung rearward, thereby ensuring thevolume of inflation and development of the airbag 30 and the energyabsorbing stroke of the airbag 30 in a fore-and-aft direction of thevehicle body. The expandable and developable airbag 30 allows an impactforce applied to the rear board 90 to be elastically received.

The inflation and development of the airbag 30 are sandwiched and heldby the elastic installation supporting members 27 that hold the airbag30 and a wide area in the swingable rear board 90, and thus developmentbehavior and development pattern are controlled and stable inflation anddevelopment are maintained. Also, the inflatable and developable airbag30 is supported by the swingable rear board 90 from the rear part side,and inflates and develops two-dimensionally, and uniform pressure isthereby applied to a wide area in the upper body Pb of the seated personPf.

In a vehicle equipped with the vehicle seat configured in this manner,when inevitability of a rear-end collision of the vehicle is predictedbased on collision occurrence information from the collision detectionsensor, a drive signal is outputted from the control unit to theinflator 29 at a predicted occurrence time of collision, the inflator 29is ignited and expanded gas jets from the inflator 29, and the airbag 30inflates and develops between the elastic installation supportingmembers 27 and the rear board 90.

As illustrated in FIG. 21, the inflated and developed airbag 30 pushesthe elastic installation supporting members 27 and the seat pad 28forward as well as pushes the rear board 90 rearward, and thus the clip92C supported on the clip retainer 92B is removed from the clipretaining hole 92 a of the retaining bracket 92A, thereby causing therear board 90 to swing.

Thus, rearward movement, due to a rear-end collision, of the upper bodyPb of the seated person Pf on the front seat 10 is elastically receivedby the airbag 30 that inflates and develops via the outer layer 31, theseat pad 28, and the elastic installation supporting members 27, and sothe rearward movement is regulated.

On the other hand, the seated person Pr on the rear seat 60 is pushedforward and moved due to vehicle body deformation by an impact of arear-end collision or rebounding after being moved rearward and pressedagainst the seat back, and for example, the knees Pn may come intocontact with the rear board 90 which is caused to be swung by inflationand development of the airbag 30. The impact force F1 at the contact ofthe knees Pn with the rear board 90 of the front seat 10 is elasticallyreceived by a wide area in the airbag 30 via the rear board 90, and thusthe upper body Pb of the seated person Pf on the front seat 10 avoidsreceiving the impact force F1 from the knees Pn of the seated person Pron the rear seat 60, thereby protecting the seated person Pf on thefront seat 10. Similarly, the impact force F1 from the knees Pn and theimpact force from the upper body of the seated person Pr moving forwardon the rear seat 60 are elastically received and protected by the airbag30 for which the volume of inflation and development is ensured.

Particularly, when the knees Pn of the seated person Pr on the rear seat60 come into contact with the rear part of the rear board 90 in aninclined manner, the contacting knees Pn are slid and moved along therear part of the rear board 90, thereby reducing the impact force F1from the knees in contact with the rear board 90. For this reason, therear board 90 may be disposed to be inclined with respect to thefore-and-aft direction of the vehicle body.

The above-described implementations each have a configuration in whichfixing of the rear board 90 by the rear board retainer 92 is released bypressing movement of the rear board 90 caused by the expanded anddeveloped airbag 30. However, when the airbag 30 inflates and develops,fixing of the rear board 90 is released beforehand so as to be swingableand thus fixing releasing operation utilizing the inflation anddevelopment of the airbag 30 is eliminated and load to the airbag 30that inflates and develops may be reduced.

Specifically, for example, instead of the rear board retainer 92 thatfixes the seat back frame 21 and the rear board 90 together, a rearboard retainer 93, which serves as a fixing releasing mechanism, isprovided as illustrated in FIG. 22. The rear board retainer 93 includesa pair of retaining brackets 93A and a locking mechanism 93B, theretaining brackets having retaining holes 93 a provided in the lowerrear face of the side brackets 24 of the seat back frame 21, the lockingmechanism for selectively moving a shaft 93 b to a locked position atwhich the shaft is inserted through the retaining holes 93 a or anunlocked position at which the shaft is retracted from the retainingholes by an electromagnetic actuator 93Ba. On the other hand, the lowerend of the rear board 90 is provided with a retaining portion 93C whichincludes a through hole 93 c and is insertable in between the pair ofretaining brackets 93A at the normal use position of the rear board 90,the retaining brackets being provided in the seat back frame 21.

In this configuration, the rear board 90 is fixed at the normal useposition by inserting the retaining portion 93C provided at the rearboard 90 into between both retaining brackets 93A provided at the seatback frame 21, and setting the shaft 93 b of the locking mechanism 93Bat the locked position by inserting the shaft 93 b into the through hole93 c of the retaining portion 93C. On the other hand, by moving theshaft 93 b of the locking mechanism 93B to the unlocked position, theshaft 93 b is retracted from the through hole 93 c and fixing isreleased.

When inevitability of a rear-end collision of a vehicle is predictedbased on collision occurrence information from the collision detectionunit, a drive signal from the control unit at a predicted occurrencetime of collision causes the electromagnetic actuator 93Ba to operate tomove the shaft 93 b to the unlocked position so that the rear board 90becomes swingable to allow the airbag 30 to inflate and develop. Thusload to inflation and development of the airbag 30 is reduced and theinflation and development of the airbag 30 may be performed moresmoothly and quickly.

It is to be noted that the rear board supporter 91 that causes the rearboard 90 to be supported on the seat back frame 21, the rear boardretainer 92, and the rear board retainer 93 serving as a fixingreleasing mechanism are not limited to the above-describedconfiguration, and may be formed by another suitable configurationhaving the above-described functions.

Fourth Implementation

A fourth implementation will be described with reference to FIGS. 23 to25. FIG. 23 is a vertical cross-sectional view illustrating the outlineof a vehicle seat; FIG. 24A is an enlarged perspective view of portion cof FIG. 23 illustrating the outline of a rear board supporter and FIG.24B is an enlarged view of portion d of FIG. 23 illustrating the outlineof a rear board retainer; and FIG. 25 is an operation explanatorydiagram of a vehicle seat when an impact occurs. It is to be noted thatthe vehicle seat in the present implementation differs from the vehicleseat in the third implementation in mounting configuration of the rearboard 90, and other major configurations are the same as those in thethird implementation. The components in FIGS. 23 to 25 corresponding tothose in FIGS. 18 to 22 are denoted by the same symbols and detaileddescription of the components is omitted and different configurationswill be mainly described.

As illustrated in FIG. 23, in the rear of the airbag 30, the upperportion of the rear board 90 disposed on the rear of the seat back 20 issupported on an upper part of the seat back frame 21 by a rear boardsupporter 95, and the lower portion of the rear board 90 is supported ona lower part of the seat back frame 21 by a rear board retainer 96.

As illustrated in FIG. 24A which is an enlarged perspective view of theportion c of FIG. 23, the rear board supporter 95 is a hat-like shapewhich is connected to the upper rear face of the right and left sidebrackets 24, and includes a supporting bracket 95A and an engagementbracket 95B, the supporting bracket having a recessed groove-shapedretaining groove 95 a at the lower end, the engagement bracketprotruding forward, being connected to upper both ends of the rear board90 and having a recessed groove-shaped engagement part 95 b which may belocked in the retaining groove 95 a of the supporting bracket 95A frombelow.

By engaging the retaining groove 95 a of the supporting bracket 95A withthe engagement part 95 b of the engagement bracket 95B, the upperportion of the rear board 90 is held at the normal use position, anddownward movement of the rear board 90 causes the engagement part 95 bof the engagement bracket 95B to be removed from the retaining groove 95a of the supporting bracket 95A, and thus the engagement is released.

As illustrated in FIG. 24B which is an enlarged perspective view of theportion d of FIG. 23, a rear board retainer 96 is a hat-like shape whichis attached to the lower end rear face of each side bracket 24, andincludes a retaining bracket 96A, a clip holder 96B, and a clip 96C, theretaining bracket including a clip retaining hole 96 a on the rear endface, the clip holder being formed in the lower both ends of the rearboard 90 in a protruding manner, the clip being mounted and supported onthe end of the clip holder.

The clip 96C mounted and supported on the clip retainer 96B is insertedand retained in the clip retaining hole 96 a of the retaining bracket96A provided in the side bracket 24, thereby fixing the lower portion ofthe rear board 90 at the normal use position. On the other hand, when aload greater than or equal to a predetermined value is applied to thefront surface of the rear board 90 from the front, along with rearwardmovement of the rear board 90, the clip 96C supported on the clipretainer 96B is removed from the clip retaining hole 96 a of theretaining bracket 96A, and thus fixing of the rear board 90 is released.

The rear board 90 is fixed at the normal use position of the rear of theseat back 20 by engaging the engagement part 95 b of the engagementbracket 95B with the retaining groove 95 a of the supporting bracket 95Afrom below and by inserting and retaining the clip 96C mounted andsupported on the clip retainer 96B into the clip retaining hole 96 a ofthe retaining bracket 96A, the engagement bracket 95B being provided inthe upper portion of the rear board 90, the supporting bracket 95A beingprovided in the upper portion of the side bracket 24, the clip retainer96B being provided in the rear board 90, the retaining bracket 96A beingprovided in the side bracket 24.

When a load greater than or equal to a predetermined value is applied tothe front surface of the rear board 90 from the front, along withrearward movement of the rear board 90, the clip 96C supported on theclip retainer 96B is removed from the clip retaining hole 96 a of theretaining bracket 96A, and the movement of the rear board 90 causes theengagement part 95 b of the engagement bracket 95B to be removed fromthe retaining groove 95 a of the supporting bracket 95A, and thus theengagement is released, which allows the rear board 90 to be detachedfrom the rear of the seat back 20.

On the other hand, when the airbag 30 inflates and develops between theelastic installation supporting members 27 and the rear board 90 due toexpanded gas injection of the inflator 29, as illustrated in FIG. 25,the airbag 30 pushes forward and urges the elastic installationsupporting members 27 and the seat pad 28 so as to allow the upper bodyPb of the seated person Pf to be elastically supported from the rearside, and the movement of the rear board 90 causes the engagement part95 b of the engagement bracket 95B to be removed from the retaininggroove 95 a of the supporting bracket 95A, and thus the engagement isreleased, which allows the rear board 90 to be detached from the rear ofthe seat back 20. Consequently, the inflation and development of theairbag 30 are sandwiched and held by the elastic installation supportingmembers 27 that hold the airbag 30 and a wide area in the rear board 90,and thus development behavior and development pattern are controlled andstable inflation and development pattern are maintained, and the amountof inflation and development and the energy absorbing stroke in thefore-and-aft direction of the vehicle body are ensured. Also, the airbag30 is supported by the detached rear board 90 from the rear part side,and inflates and develops two-dimensionally, and uniform pressure isthereby applied to a wide area in the upper body Pb of the seated personPf.

In a vehicle equipped with the vehicle seat configured in this manner,when inevitability of a rear-end collision of the vehicle is predictedbased on collision occurrence information from the collision detectionunit, a drive signal is outputted from the control unit to the inflator29 at a predicted occurrence time of collision, expanded gas jets fromthe inflator 29, and the airbag 30 inflates and develops between theelastic installation supporting members 27 and the rear board 90.

The inflated and developed airbag 30 pushes the elastic installationsupporting members 27 and the seat pad 28 forward, whereas the clip 96Csupported on the clip retainer 96B is removed from the clip retaininghole 96 a of the retaining bracket 96A, and the movement of the rearboard 90 causes the engagement part 95 b of the engagement bracket 95Bto be removed from the retaining groove 95 a of the supporting bracket95A, and thus the engagement is released and the rear board 90 movesrearward.

Thus, rearward movement, due to a rear-end collision, of the upper bodyPb of the seated person Pf on the front seat 10 is elastically receivedby the airbag 30 that inflates and develops via the outer layer 31, theseat pad 28, and the elastic installation supporting members 27, and sothe rearward movement is regulated.

On the other hand, when the rear board 90 is pushed rearward by theinflation and development of the airbag 30, the seated person Pr on therear seat 60 may come into contact with the rear board 90 of the frontseat 10, for example, at the knees Pn. The impact force F1 at thecontact of the knees Pn with the rear board 90 of the front seat 10 iselastically received by a wide area in the airbag 30 via the rear board90, and thus the upper body Pb of the seated person Pf on the front seat10 avoids receiving the impact force F1 from the knees Pn of the seatedperson Pr on the rear seat 60, thereby protecting the seated person Pfon the front seat 10. Similarly, the impact force F1 from the knees Pnand the impact force from the upper body of the seated person Pr movingforward on the rear seat 60 are elastically received and protected bythe airbag 30 for which the volume of inflation and development and theenergy absorbing stroke are ensured.

Although the above-described implementations each have a configurationin which fixing of the rear board 90 with the rear board retainer 96 isreleased by the pressure caused by the inflation and development of theairbag 30, instead of the rear board retainer 96, for example, a rearboard retainer similar to the rear board retainer 93 illustrated in FIG.22 may be provided. When the airbag 30 inflates and develops at apredicted occurrence time of collision, releasing the fixing of the rearboard 90 beforehand allows the rear board 90 to be moved, and thus it isunnecessary to release the fixing of the rear board 90 by the movementof the rear board 90 which is caused by the airbag 30, and thus load tothe airbag 30 at the inflation and development may be reduced.

Fifth Implementation

A fifth implementation will be described with reference to FIGS. 26 and27. It is to be noted that FIGS. 26 and 27 correspond to FIGS. 18 and21, and the present implementation differs from the third implementationin mounting configuration of the rear board 90, and other majorconfigurations are the same as those in the third implementation. Thecomponents in FIGS. 26 and 27 corresponding to those in FIGS. 18 and 21are denoted by the same symbols and detailed description of thecomponents is omitted and different configurations will be mainlydescribed.

As illustrated in FIG. 26, in the outer layer 31 of the seat back 20,the airbag 30 is covered by the elastic rear part 33, and the rear board90 is disposed in the rear of the rear part 33. The rear board 90 has arectangular tubular shape that covers the airbag 30, and includesfragile portions 90 a which are each a groove or a thin layer tofacilitate predetermined bending deformation.

When the airbag 30 inflates and develops two-dimensionally between theelastic installation supporting members 27 and the rear part 33 of theouter layer 31 due to expanded gas injection of the inflator 29, asillustrated in FIG. 27, the airbag 30 pushes forward and urges theelastic installation supporting members 27 and the seat pad 28, andcauses the rear part 33 of the outer layer 31 and the rear board 90 toexpand so as to sufficiently ensure the volume of inflation anddevelopment of the airbag 30 and the energy absorbing stroke of theairbag 30. The inflation and development of the airbag 30 are sandwichedand held by the elastic installation supporting members 27 that hold theairbag 30, and extending, expanding rear part 33 of the outer layer 31and the rear board 90, and thus development behavior and developmentpattern are controlled and stable inflation and development pattern ismaintained. Also, the airbag 30 is supported by the rear board 90 fromthe rear part side, and inflates and develops two-dimensionally, anduniform pressure is thereby applied to a wide area in the upper body Pbof the seated person Pf.

In a vehicle equipped with the vehicle seat configured in this manner,when inevitability of a rear-end collision of the vehicle is predictedbased on signals from the collision detection unit, a drive signal isoutputted from the control unit to the inflator at a predictedoccurrence time of collision, expanded gas jets from the inflator, andthe airbag 30 inflates and develops between the elastic installationsupporting members 27 and the rear part 33 of the outer layer 31 asillustrated in FIG. 27. Thus, rearward movement, due to a rear-endcollision, of the upper body Pb of the seated person Pf on the frontseat 10 is elastically received by the airbag 30 via the outer layer 31,the seat pad 28, and the elastic installation supporting members 27, andso the rearward movement is regulated.

On the other hand, the seated person Pr on the rear seat 60 may be movedforward and, for example, the knees Pn may come into contact with therear board 90 of the front seat 10. At this point, the knees Pn areelastically received via the outer layer 31 and the rear board 90 by theairbag 30 which has expanded and developed between the elasticinstallation supporting members 27, and the rear part 33 of the outerlayer 31, the rear board 90, and thus forward movement is restrained andthe upper body Pb of the seated person Pf on the front seat 10 avoidsreceiving the impact force F1 from the knees Pn of the seated person Pron the rear seat 60. Similarly, the knees Pn and the upper body of theseated person Pr moving forward on the rear seat 60 are elasticallyreceived and protected by the airbag 30 which has inflated anddeveloped.

Also when the rear board 90 is damaged due to an impact, the airbag 30is held by the outer layer 31 and the development behavior anddevelopment pattern of the inflation and development of the airbag 30are controlled, and stable inflation development pattern is maintained.

Thus, according to each of the third to fifth implementations describedabove, with a simple configuration in which the airbag disposed betweenthe seat pad and the rear board within the seat back inflates anddevelops to push the rear board rearward, the airbag, which is supportedby the rear board and inflates and develops, makes it possible toelastically receive rearward movement of a seated person due to acollision by uniform pressure over a wide area and to protect the seatedperson against an impact from the rear, thereby enabling directprotection of a seated person by the airbag at the time of a collisionand accurate reduction of an impact from the rear of the seat back.

In the above description, the case is taken as an example in which theairbag 30 is caused to inflate and develop by a single inflator.However, the airbag 30 may be caused to inflate and develop in multiplesteps in a suitable manner to a seated person. For example, the airbag30 is caused to inflate and develop in multiple steps using a pluralityof inflators in a suitable manner to a seated person so that thedevelopment state of the airbag 30, such as an inflation developmentpressure and a development time may also be controlled.

Sixth Implementation

A sixth implementation will be described with reference to FIGS. 28 and29. FIG. 28 is a schematic rear view with partial cutaway illustratingthe outline of the present implementation; and FIG. 29 is across-sectional view of FIG. 28 taken along line XXIX-XXIX. It is to benoted that the components corresponding to those in the firstimplementation are denoted by the same symbols as in FIGS. 1 to 5 anddetailed description of the components is omitted.

As illustrated in FIGS. 28 and 29, the inflator 29 is attached to a sideframe 23 or a side bracket 24 outwardly in the vehicle body so as tolocated inwardly of the seat back frame 21. As illustrated in FIG. 29,the inflator 29 is disposed so as to be located forward of the airbag 30with the elastic installation supporting members 27 interposedtherebetween in the fore-and-aft direction of the vehicle body.

With this configuration, in the case where the airbag 30 inflates anddevelops within the seat back 20 due to a collision, the reactive forceis received by the elastic installation supporting members 27, and thusprevention effect on interference between the airbag 30 and the inflator29 is obtained.

Seventh Implementation

A seventh implementation will be described with reference to FIGS. 30 to32. FIG. 30 is a schematic cross-sectional view of the front seat 10;FIG. 31 is a schematic perspective view with partial cutaway of thefront seat 10 as seen from the rear; and FIG. 32 is an operationexplanatory diagram of the front seat 10 when an impact occurs. It is tobe noted that the components corresponding to those in the firstimplementation are denoted by the same symbols as in FIGS. 1 to 5 anddetailed description of the components is omitted. In the presentimplementation, the inflator 29 is not attached to a side bracket 24. Asillustrated in FIGS. 30 and 31, the inflator 29 is disposed in parallelto the upper cross member 25 and fixed thereto so that thecircumferential surface of the inflator 29 is in contact withsubstantially the central position of the upper cross member 25 in theextending direction. Therefore, the inflator 29 is attached within theseat back frame 21 and to an upper portion of the seat back frame 21.

In the case where another vehicle collides with a vehicle having thefront seat 10, the inflator 29 is ignited by an operation of a collisiondetection unit or collision information predicted by a collisionprediction unit, and expanded gas from the inflator 29 causes the airbag30 to instantly inflate and develop between the elastic installationsupporting members 27 and the rear surface of the seat back 20 asillustrated in FIG. 32.

In this process, the front of the airbag 30 is covered with flexiblematerials such as the elastic installation supporting member 27, theseat pad 28, and the outer layer 31, and thus due to the inflation anddevelopment of the airbag 30, as illustrated in FIG. 32, these flexiblematerials exhibit slight deformation in the forward direction of thevehicle body, whereas the outer layer 31, which covers the rear of theairbag 30 as a flexible material, exhibits significantly protrudingdeformation in the rearward direction of the vehicle body.

With the front seat 10, the deformation behavior of the flexible membersand flexible materials in front and in rear of the airbag 30 allows thevolume E of development of the airbag 30 in the fore-and-aft directionof the vehicle body to be ensured, and also allows the energy absorbingstroke of the seat back 20 in the fore-and-aft direction of the vehiclebody to be sufficiently ensured.

That is, as illustrated in FIG. 32, rearward movement, due to an impactof a rear-end collision, of the upper body Pb of the front seat personPf is elastically received by the outer layer 31 at the front of theseat back 20, the seat pad 28, the elastic installation supportingmembers 27, and the inflated and developed airbag 30, and thus the upperbody Pb of the front seat person Pf is protected against the impact tobe received when being pressed against the seat back 20.

On the other hand, due to an impact of a rear-end collision, the rearseat person Pr is pressed against the rear seat 60, and is moved forwardby subsequent rebound. Due to the rebound, the knees Pn of the rear seatperson Pr moving forward is elastically received by the outer layer 31on the rear of the seat back and the airbag 30, and thus the upper bodyPb of the seated person Pf on the front seat 10 is protected against thecollision impact of the knees Pn of the rear seat person Pr.

In this process, the airbag 30 is restrained to some extent by theinternal geometry within the seat back 20 located immediately rearwardof the upper body Pb of the seated person Pf on the front seat 10, anddevelopment behavior and development pattern are controlled and theairbag 30 is caused to stably inflate and develop. Consequently,rearward movement of the upper body Pb of the seated person Pf may bereliably received, and the impact due to forward movement of the kneesPn of the rear seat person Pr may be reliably absorbed, and thus properprotection for the seated person Pf may be achieved.

In addition, such protection of the seated person Pf is achieved by theairbag 30 that inflates and develops within the seat back 20 anddisposition of the flexible materials in front and in rear of the airbag30 (that is, the outer layer 31, the seat pad 28, and the elasticinstallation supporting members 27), and thus the configuration issignificantly simplified.

Furthermore, because the supporting rigidity of the inflator 29 isensured due to the fixing thereof to the upper cross member 25, and theupper cross member 25 is located in the upper portion of the seat backframe 21, the internal space of the seat back for the airbag 30 toinflate and develop is not interfered by the inflator 29, and thus anairbag development space for absorbing an impact at the time of acollision is ensured.

Moreover, the inflator 29 is disposed within the seat back frame 21which is formed in a substantially rectangular frame shape, and thus theinflator 29 is protected against an external force by the seat backframe 21 and protrusion of the inflator 29 outwardly of the seat backframe 21 is avoided. Moreover, the inflator 29 may be integrally formedwith the airbag 30 which is provided within the seat back frame 21.

Eighth Implementation

Next, an eighth implementation will be described with reference to FIGS.33 and 34. In the seventh implementation, the case has been describedwhere an inflator is used and an airbag is caused to inflate anddevelop. However, in the eighth seventh implementation, the case will bedescribed where two inflators are used and an airbag is caused toinflate and develop.

FIG. 33 is a schematic perspective view with partial cutaway of thefront seat 10 as seen from the rear; and FIG. 34 is a fragmentaryperspective view with partial cutaway of the front seat 10. Asillustrated in FIG. 33, in the front seat 10 according to the presentimplementation, the entire configuration of the seat back 20 is the sameas that of the seventh implementation except for the configuration ofthe inflator, and thus detailed description is omitted.

As illustrated in FIGS. 33 and 34, the inflator 29 is fixedly mountedwithin each of the cylindrical upper cross member 25 and the cylindricallower cross member 26.

As illustrated in FIG. 34, the mounting of the inflator 29 within thelower cross member 26 is achieved by having the outer circumferentialsurface of the cylindrical inflator 29 in contact with the innercircumferential surface of the lower cross member 26 and firmly fixingthem together with a fixing bracket (not illustrated).

As illustrated in FIG. 34, the portion of the outer circumferentialsurface of the inflator 29 corresponding to the lower cross member 26 isprovided with a plurality of small holes 26 a, and a gas suction inlet(not illustrated) is provided so that expanded gas from the inflator 29passes through the small holes 26 a and is introduced into the airbag30.

The mounting of the inflator 29 within the upper cross member 25 isachieved similarly to the mounting within the lower cross member 26 anddescription is omitted. Expanded gas jets through the small holes 25 aopened in the upper cross member 25.

According to the present implementation, in the case where anothervehicle collides with a vehicle having the front seat 10, the airbag 30which has inflated and developed due to an operation of each inflator29, the outer layer 31 on the rear of the seat back 20, the seat pad 28,and the elastic installation supporting members 27 elastically receiverearward movement of the upper body Pb of the front seat person Pf, andthus the upper body Pb of the seated person Pf is protected.

On the other hand, the knees Pn of the rear seat person Pr movingforward due to a rear-end collision of a vehicle is elastically receivedby the outer layer 31 on the rear of the seat back 20 and the inflatedand developed airbag 30, and thus the upper body Pb of the front seatperson Pf is protected against the collision impact of the knees Pn ofthe rear seat person Pr. Therefore, similarly to the seventhimplementation, proper protection for the seated person Pf is achievedand the configuration is significantly simplified.

Also, because each inflator 29 is fixed within the upper cross member 25and the lower cross member 26, part of the bending strength and torsionstrength of the upper cross member 25 and the lower cross member 26 isprovided by the inflator 29, and thus the bending rigidity and torsionrigidity of the cross members 25, 26 are reinforced. Therefore, as aresult, the seat back frame 21 is reinforced and torsion and strain ofthe seat back 20 is reduced.

Furthermore, the inflator 29 does not protrude from the seat back frame21, and thus even when the inflator 29 is mounted in the seat back frame21, a driver does not feel uncomfortable while being seated, andinflation and development of the airbag 30 is not prevented by theinflator 29.

Moreover, with this configuration, the inflators 29 disposed above andbelow may be operated with a time lag. By operating of the inflators 29with a time lag, the inflation and development state of the airbag 30may be continued longer compared with the case where the inflators 29are operated simultaneously or the case where an inflator with a singlestep is operated. Thus energy absorbing effect of the airbag may lastfor a longer time.

Although the present implementation adopts a configuration in which oneairbag 30 is used, two airbags may be used. FIG. 35 is a schematic rearview with partial cutaway for explaining a modification of the presentimplementation; and FIG. 36 is an operation explanatory diagram of thefront seat 10 when an impact occurs according to the modification.

As illustrated in FIG. 35, in the present modification, the airbag 30includes an upper airbag 30 a and a lower airbag 30 b, the upper airbagbeing disposed on the upper side of the space between the elasticinstallation supporting members 27 and the outer layer 31 on the rear ofthe seat back 20 within the seat back 20, the lower airbag beingdisposed on the lower side of the space. Each airbag is inflatably anddevelopably retained, for example, on the outer layer 31 by a retainingunit (not illustrated).

The upper airbag 30 a has upper and lower ends, the upper end beinglocated at the height of the upper cross member 25, the lower end beinglocated at the height of approximately the midpoint between the uppercross member 25 and the lower cross member 26. The upper airbag 30 a isa bag body which is a substantially rectangular shape in a plan view andhas a width with crosswise ends located close to the right and left sideframes 23 and side brackets 24, the bag body being compressed and foldedin the fore-and-aft direction of the seat back 20.

The lower airbag 30 b has upper and lower ends, the lower end beinglocated at the height of the lower cross member 26, the upper end beinglocated at the height of approximately the midpoint between the uppercross member 25 and the lower cross member 26. The lower airbag 30 b isa bag body having a width similar to the width of the upper airbag 30 a,the bag body also being compressed and folded in the fore-and-aftdirection of the seat back 20.

Both airbags 30 a, 30 b are disposed so as to be partially overlappedwith each other to prevent a space therebetween when the both airbagsinflate and develop.

With this configuration, when both upper and lower inflators 29 areoperated, even when the position of the knees Pn of the rear seat personPr is varied to some extent, the knees may be reliably received by theairbags 30 a, 30 b located above and below as illustrated in FIG. 36,and thus an impact from the rear may be received more reliably comparedwith the case where one airbag is used.

In addition, the inflation and development pattern of the entire airbag30 is controllable by controlling on and off of the ignition of theinflators 29.

Ninth Implementation

A ninth implementation will be described with reference to FIGS. 37 to39. FIG. 37 is a schematic explanatory cross-sectional view of the frontseat 10; FIG. 38 is a schematic perspective view with partial cutaway ofthe front seat 10 as seen from the rear; and FIG. 39 is an operationexplanatory diagram when an impact occurs.

The disposition and configuration of the inflator 29 according to thepresent implementation will be described. As illustrated in FIG. 37,bending portions between the upper frame 22 and the side frames 23 inthe seat back frame 21 are each a corner or curved portion 21 a which isobtained by curving or bending a tube frame. The connecting portionbetween each side bracket 24 and the lower cross member 26 is a cornerportion 21 b which is created when the lower cross member 26 isinstalled between the side brackets 24. Also, the connecting portionbetween each side frame 23 and the upper cross member 25 is a cornerportion 21 c which is created when the upper cross member 25 isinstalled between the side frames 23.

As illustrated in FIG. 38, two inflators 29 are mounted in the upperportion and the lower portion of the seat back frame 21, respectively.The inflator 29 mounted in the upper portion of the seat back frame 21has one end 101 a and the other end 101 b, the one end 101 a being fixedto the upper cross member 25 in the vicinity of one corner portion 21 c,the other end 101 b being fixed to a linear portion 101 c of a bracket101 which is secured to the side frame 23 in the vicinity of the cornerportion 21 c.

Similarly, the inflator 29 mounted in the lower portion of the seat backframe 21 has one end 102 a and the other end 102 b, the one end 102 abeing fixed to the lower cross member 26 in the vicinity of one cornerportion 21 b, the other end 102 b being fixed to a linear portion 102 cof a bracket 102 which is secured to the side bracket 24 in the vicinityof the corner portion 21 b.

Thus, both inflators 29 are respectively provided in the corner portions21 c, 21 b which are on the diagonal of a rectangular shape includingthe upper cross member 25, the side frames 23, the side brackets 24, andthe lower cross member 26.

In a vehicle having the front seat 10 according to the presentimplementation having the above configuration, each inflator 29 isignited by an operation of a collision detection unit or collisioninformation predicted by a collision prediction unit, and expanded gasfrom the inflator 29 thereby causes the airbag 30 to instantly inflateand develop between the elastic installation supporting members 27 andthe rear surface of the seat back 20 as illustrated in FIG. 39.

In this process, the front of the airbag 30 is covered with flexiblematerials such as the elastic installation supporting member 27, theseat pad 28, and the outer layer 31, and thus due to the inflation anddevelopment of the airbag 30, these flexible materials exhibit slightdeformation in the forward direction of the vehicle body in FIG. 39,whereas the outer layer 31, which covers the rear of the airbag 30 as aflexible material, exhibits significantly protruding deformation in therearward direction of the vehicle body.

In this process, the above-mentioned deformation behavior of theflexible members and flexible materials in front and in rear of theairbag 30 allows the volume E of development of the airbag 30 in thefore-and-aft direction of the vehicle body to be ensured, and alsoallows the energy absorbing stroke of the seat back 20 in thefore-and-aft direction of the vehicle body to be sufficiently ensured.

That is, as illustrated in FIG. 32, rearward movement, due to an impactof a rear-end collision, of the upper body Pb of the seated person Pf onthe front seat 10 is elastically received by the outer layer 31 at thefront of the seat back 20, the seat pad 28, the elastic installationsupporting members 27, and the inflated and developed airbag 30, andthus the upper body of the seated person Pf on the front seat 10 isprotected against the impact to be received when being pressed againstthe seat back 20 of the seat due to a rear-end collision.

On the other hand, due to an impact of a rear-end collision, the personPr on the rear seat 60 is pressed against the rear seat, and is movedforward by subsequent rebound. Due to the rebound, the knees Pn of therear seat person Pr moving forward is elastically received by the outerlayer 31 on the rear of the seat back 20 and the airbag 30, and thus theupper body Pb of the seated person Pf on the front seat 10 is protectedagainst the collision impact of the knees Pn of the rear seat person Pr.

In this process, the airbag 30 is controlled by the internal geometrywithin the seat back 20 located immediately rearward of the upper bodyPb of the seated person Pf on the front seat 10, and is caused to stablyinflate and develop. Consequently, rearward movement of the upper bodyPb may be reliably received, and the impact due to forward movement ofthe knees Pn of the rear seat person Pr may be reliably absorbed, andthus proper protection for the seated person Pf may be achieved.

In addition, such protection of the seated person Pf is achieved by theairbag 30 that inflates and develops within the seat back 20 anddisposition of the flexible materials in front and in rear of the airbag30 (that is, the outer layer 31, the seat pad 28, and the elasticinstallation supporting members 27), and thus the configuration issignificantly simplified.

In addition, because the inflators 29 are mounted in the corner portions21 c and 21 b of the seat back frame 21 in a substantially frame shape,inflation and development of the airbag 30 is not prevented by theinflators 29, and the torsion rigidity of the corner portions 21 c and21 b, which are likely to receive a stress at the time of a vehiclecollision, is reinforced by the inflators 29.

Furthermore, the inflators 29 are bridged between both side positions(that is, between a position of the upper cross member 25 and a positionof the side frame 23, and a position of the lower cross member 26 and aposition of the side bracket 24) of the seat back frame 21 via thebrackets 101 and 102 across the corner portions 21 c and 21 b, and thusa reactive force to the jet of gas from each inflator 29 may beeffectively distributed from both side positions of the seat back frame21 to the entire seat back frame 21. Also, each inflator 29 is locatedat a corner of the rectangular shape including the upper cross member25, the side frames 23, the side brackets 24, and the lower cross member26, and so even when the seat back 20 is equipped with a side air bag oran active headrest mechanism, the inflators 29 may be disposed atpositions that do not interfere with the side air bag or the activeheadrest mechanism.

Furthermore, with this configuration, the inflators 29 disposed in theupper portion and the lower portion of the seat back frame 21 may beoperated with a time lag. By operating of the inflators 29 with a timelag, the airbag 30 may be caused to inflate and develop at a slowerspeed compared with the case where the inflators 29 are operatedsimultaneously or the case where an inflator with a single step isoperated. Thus, load to a passenger due to development of the airbag maybe reduced.

Moreover, the inflation and development state of the airbag may becontinued longer compared with the case where the inflators are operatedsimultaneously or the case where an inflator with a single step isoperated. Thus energy absorbing effect of the airbag may last for alonger time.

Tenth Implementation

Next, a tenth implementation will be described with reference to FIGS.40 and 41. In the ninth implementation, the case has been describedwhere two inflators are used and an airbag is caused to inflate anddevelop. However, in the tenth seventh implementation, the case will bedescribed where four inflators are used and four airbags are caused toinflate and develop.

FIG. 40 is a schematic perspective view with partial cutaway of thefront seat 10 as seen from the rear; and FIG. 41 is a schematiccross-sectional view of the operation state of the front seat 10 at thetime of an offset collision, the cross-sectional view corresponding to across-section along line XXXXI-XXXXI in FIG. 40.

As illustrated in FIG. 40, in the front seat 10, the entireconfiguration of the seat back 20 is the same as that of the ninthimplementation except for the configuration of the inflators and airbags, and thus detailed description is omitted.

As illustrated in FIG. 40, the inflators 29 are in all the respectivecorners (that is, the corner portions 21 c and 21 b at four corners) ofthe rectangular shape including the upper cross member 25, the sideframes 23, the side brackets 24, and the lower cross member 26 viabrackets 103, 104, 105, and 106. These brackets have the sameconfiguration as that of the brackets 101 and 102 according to the ninthimplementation.

Four airbags 30 (hereinafter denoted as airbags 30 c, 30 d, 30 e, and 30f) are disposed which are obtained by dividing a rectangular shape intofour equal rectangular-shaped parts by the midpoints of the frames andthe cross members in a rear view, the rectangular shape including theupper cross member 25, the side frames 23, the side brackets 24, and thelower cross member 26 within the substantially rectangular frame-shapedseat back frame 21. Each airbag is inflatably and developably retained,for example, on the outer layer 31 by a retaining unit (notillustrated).

The airbags 30 c, 30 d, 30 e, and 30 f are connected to the respectiveinflators 29 located at four corners of the above-mentioned rectangularshape in the seat back frame 21 via respective gas suction inlets (notillustrated), and are disposed so as to be partially overlapped witheach other to some extent to prevent a space between airbags 30 when allthe airbags 30 inflate and develop.

The front seat 10 allows, for example, the above-mentioned collisiondetection unit (not illustrated) or collision prediction unit to detectcollision information, and according to the information, causes acontrol unit (not illustrated) to control a inflator 29 to be ignited,and appropriate airbag(s) out of four airbags are selectively caused toinflate and develop at the time of a collision. If some of the airbags30 have a higher load, the load may be reliably absorbed. This iseffective for example when an offset collision occurs.

As a specific example, the case will be described where a vehicleexperiences a rear-end collision from the rear left. First, when avehicle experiences a rear-end collision from the rear left, the vehicleexhibits yawing to the forward right, and the upper body Pb of theseated person Pf on the front seat 10 is pressed against the seat back20 to the rear left. Similarly, the upper body of the seated person Pron the rear seat is pressed against to the rear left, then the knees arethrown to the forward left by subsequent rebound.

In this process, the collision detection unit (not illustrated) or thecollision prediction unit recognizes a rear-end collision from the rearleft, and the inflators 29 to be ignited are limited to the twoinflators 29 located inwardly along the vehicle width in the seat back20 by a control unit (not illustrated) based on recognized collisioninformation. As illustrated in FIG. 41, two airbags 30 c and 30 d arecaused to inflate and develop, thereby making it possible to reliablyreceive movement of the upper body Pb of the seated person Pf to therear left (that is, in the direction of arrow A) and movement of theknees Pn of the seated person Pr to the forward left (that is, in thedirection of arrow B).

Therefore, with the front seat 10 according to the presentimplementation, it is possible to individually control multiple airbags30 in conjunction with a collision, and only necessary airbags 30 areselectively caused to inflate and develop according to the type of acollision as described above, and thus an impact may be absorbedaccurately.

Furthermore, a truss structure may be constructed in which each of theinflators 29 is bridged over a corresponding one of the four corners ofthe rectangular shape of the seat back frame 21, and thus the inflationand development of each airbag 30 is not prevented by the structure andthe rigidity of the seat back frame 21 is reinforced.

The four airbags 30 disposed within a substantially rectangular shape ofthe seat back frame 21 are each caused to inflate and develop by anindividual inflator 29, and thus a larger reactive force of the airbagmay be ensured compared with the case where the volume corresponding tothe combined volume of the four airbags 30 c to 30 f is caused toinflate and develop with an inflator 29.

It is to be noted that the present disclosure is not limited to theabove-described implementations, and various modifications may be madewithout departing from the scope of the present disclosure. For example,the first implementation adopts a configuration in which the inflator 30is mounted on the side bracket 24 outwardly in the vehicle body width.However, it is also possible to mount the inflators 30 both on the sidebracket 24 outwardly in the vehicle body width and on the side bracket24 inwardly in the vehicle body width. With this configuration,operating the inflators 29 with a time lag makes it possible to changethe duration of inflation and development and the amount of inflationand development of each airbag.

Furthermore, in each implementation, the vehicle has the front seat 10and the rear seat 60 that are arranged side by side. However, the rearseat 60 is not a required component. For example, the rear of the frontseat 10 may serve as a loading bed. Also in this case, it is possible toprotect a seated person on the vehicle seat 10 against an impact by theinflation and development of the airbag 30, the impact being generatedby a loaded object on the loading bed, which is moved forward due to avehicle collision to collide with the rear of the seat back 30.

In the eighth implementation, a configuration has been illustrated inwhich the inflator 29 is mounted to the upper cross member 25. However,the inflator 29 may be disposed at a location outwardly in the vehiclewidth direction of the positions in the upper frame 22, at which thecylindrical stay brackets 42 are formed, the location being outward ofthe seat back frame 21. With this configuration, interference betweenthe airbag 30 which inflates and develops and each inflator iscompletely avoidable, and thus stable development of the airbag 30 isensured.

When an inflator is mounted in the upper portion of the seat back frame21, it is also optional to use an inflator which causes an airbag foractive headrest to inflate and develop.

In the ninth implementation, the inflator 29 is mounted in the cornerportions 21 c or 21 b. However, without being limited to these portions,the inflator 29 may be mounted to one of the corner or curved portions21 a between the upper frame 22 and the side frames 23, the corner orcurved portions 21 a being obtained by curving or bending a tube frame.

What is claimed is:
 1. A vehicle seat airbag system, comprising: anairbag which is caused by a vehicle seat airbag system to inflate anddevelop within a seat back, wherein the airbag is disposed between aseat pad and a rear board provided in a rear of the seat back, andwherein inflation and development of the airbag in the seat back allowsthe airbag to elastically support an upper body of a seated person, andcauses the rear board to be pushed rearwardly to allow the airbag toelastically receive an impact force which is applied to the rear board.2. The vehicle seat airbag system according to claim 1, wherein the rearboard is supported on the rear of the seat back swingably in a directionaway from the rear of the seat back.
 3. The vehicle seat airbag systemaccording to claim 1, wherein the rear board is removed from the rear ofthe seat back by pushing.
 4. The vehicle seat airbag system accordingclaim 1, wherein the rear board is removably fixed to the rear of theseat back and includes: a collision prediction unit that predicts acollision to a vehicle; and a fixing release mechanism that releasesfixing based on information of collision occurrence which is predictedby the collision prediction unit.
 5. The vehicle seat airbag systemaccording to claim 1, wherein an outer layer is interposed between theairbag and the rear board, the outer layer being caused by the inflatedand developed airbag to expand rearwardly, and the outer layer beingprovided with the rear board.
 6. The vehicle seat airbag systemaccording to claim 1, wherein the rear board includes a fragile part. 7.The vehicle seat airbag system according to claim 1, further comprising:a control unit that controls the inflation and development of theairbag; and a collision detection unit that detects a collision to avehicle, wherein the control unit causes the airbag to inflate anddevelop after a predetermined time delay since the collision detectionunit detects a collision.
 8. The vehicle seat airbag system according toclaim 1, further comprising: a control unit that controls the inflationand development of the airbag; and a collision prediction unit thatpredicts a collision to a vehicle, wherein the control unit starts tocause the airbag to inflate and develop at a time which is determinedbased on a time of collision occurrence predicted by the collisionprediction unit.
 9. The vehicle seat airbag system according to claim 1,wherein the airbag inflates and develops in multiple steps within theseat back.